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I'm thinking that back then nephilims took the shape of giants because they were most powerful, but now could they be taking a normal size but rule from the top by intelligence? Do you think some of the elites there can be nephilims? I guess nephilims are usually cannibals too, that explains those elites' behaviour. Perhaps some "humans" we see today in our daily life are not even humans?

I don't believe that. The purpose of the Flood, some speculate, was to kill off these abominable Nephalim, which God succeeded in doing. You can still see some traces of giantism in people today (and even in some like Goliath), but that wouldn't be from the Nephalim as, presumably, Noah's line was pure in body and soul. Hence why he and his progeny were saved, because they were continuing the pure Messianic bloodline from Adam, as well as preserving the true Faith, to bring forth Our Lord Jesus Christ. Rather, I would speculate that before the Deluge the fallen angels manipulated certain genetic markers in these "sons of God" to bring forth the Giants/Nephalim.

What I said previously about the size depictions in ancient Egypt, Mesopotamia, etc., I argue, comes from a memory of these giants of the ante-Diluvian world. Which is also contained within the feats associated with the deities of the various Indo-European religions.

This idea that the bloodline of the Nephalim persists today gets into the weird Protestant errors of the "Serpent seed" and whatnot.

I also wanted to post what Anne-Catherine Emmerich saw in regard to the ante-Diluvian giants:

We must not picture to ourselves the earth before the Deluge as it is now. Palestine was by no means so broken up by valleys and ravines. Plains were far more extensive, and single mountains less lofty. The Mount of Olives was at that time only a gentle rising. The Crib Cave of Bethlehem was as later a wild cavern, but the surroundings were different.

The people of those early times were larger. though not out of proportion. We would regard them with astonishment, but not with fright, for they were far more beautiful in form than people of a later period. Among the old marble statues that I see in many places lying in subterranean caves, may be found similar figures.

Cain led his children and grandchildren to the region pointed out to him, and there they separated. Of Cain himself, I have never seen anything more that was sinful. His punishment appeared to consist in hard, but fruitless labor. Nothing in which he was personally engaged succeeded. I saw that he was mocked and reviled by his children and grandchildren, treated badly in every way. And yet they followed him as their leader, though as one accursed. I saw that Cain was severely punished, but not damned.

One of Cain's descendants was Thubalcain, the originator of numerous arts, and the father of the giants. I have frequently seen that, when the angels fell, a certain number had a moment of repentance and did not in consequence fall as low as the others. Later on, these fallen spirits took up their abode on a high, desolate, and wholly inaccessible mountain whose site at the time of the Deluge became a sea, the Black Sea, I think. They were permitted to exercise their evil influence upon men in proportion as the latter strayed further from God. After the Deluge they disappeared from that region, and were confined to the air. They will not be cast into Hell before the last day.

I saw Cain's descendants becoming more and more godless and sensual. They settled further and further up that mountain ridge where were the fallen spirits. Those spirits took possession of many of the women, ruled them completely, and taught them all sorts of seductive arts. Their children were very large. They possessed a quickness, an aptitude for everything, and they gave themselves up entirely to the wicked spirits as their instruments. And so arose on this mountain and spread far around, a wicked race which by violence and seduction sought to entangle Seth's posterity likewise in their own corrupt ways. Then God declared to Noe His intention to send the Deluge. During the building of the ark, Noe had to suffer terribly from those people.

I have seen many things connected with the race of giants. They could with ease carry enormous stones high up the mountain, they could accomplish the most stupendous feats. They could walk straight up trees and walls just as I have seen others possessed by the devil doing. They could effect the most wonderful things, they could do whatever they wished; but all was pure jugglery and delusion due to the agency of the demon. It is for that reason that I have such horror of every species of jugglery and fortune-telling. These people could form all kinds of images out of stone and metal; but of the knowledge of God they had no longer a trace. They sought their gods in the creatures around them. I have seen them scratch up a stone, form it into an extravagant image, and then adore it. They worshipped also a frightful animal and all kinds of ignoble things. They knew all things, they could see all things, they were skilled in the preparing of poisons, they practiced sorcery and every species of wickedness. The women invented music. I saw them going around among the better tribes trying to seduce them to their own abominations. They had no dwelling houses, no cities, but they raised massive round towers of shining stone. Under those towers were little structures leading into great caverns wherein they carried on their horrible wickedness. From the roofs of these structures, the surrounding country could be seen, and by mounting up into the towers and looking through tubes, one could see far into the distance. But it was not like looking through tubes made to bring distant objects into view. The power of the tubes to which I here allude, was effected by satanic agency. They that looked through them could see where the other tribes were settled. Then they marched against them, overcame them, and lawlessly carried all before them. That same spirit of lawlessness they exercised everywhere. I saw them sacrificing children by burying them alive in the earth. God overthrew that mountain at the time of the Deluge.

Henoch, Noe's ancestor, opposed that wicked race by his teachings. He wrote much. Henoch was a very good man and one very grateful to God. In many parts of the open fields, he raised altars of stone and there the fruits of the earth flourished. He gave thanks to God and offered sacrifice to Him. Chiefly in his family was religion preserved and handed down to Noe. Henoch was taken up to Paradise. There he waits at the entrance gate, whence with another (Elias) he will come again before the last day.

Cham's descendants likewise had similar relations with the evil spirits after the Deluge, and from such connection sprang so many demoniacs and necromancers. so many mighty ones of the world, so many great, wild, daring men.

Semiramis herself was the offspring of demoniacs, consequently she was apt at everything save the working out of her salvation.

Later on, there arose another people esteemed as gods by the heathens. The women that first allowed themselves to be ruled by evil spirits were fully conscious of the fact, though others were ignorant of it. These women had it (the principle of possession) in them like flesh and blood, like original sin.
-Anne-Catherine Emmerich, Life of Our Lord Jesus Christ, II.5. p.30-33

I don't see how Anne Catherine Emmerich is contradicting Enoch's story, whom she praises as a holy man.  It's unclear what she means when she says "when the angels fell".  Is she talking about satan's revolt against God vs St Michael?  I don't see how because she says they won't be cast into hell before the last day.  But satan and his angels are already in hell.  So she must be talking about fallen angels in the same way that Enoch was, which means, angels fell a 2nd time.  She uses the term (assuming the translation is accurate) of "fallen spirits".  But satan and co are not fallen spirits but demons who are in hell.  So, it appears that the "sons of god" does mean actual angels.

Yeah, in a way, it almost confuses things again. As she goes on to say:

I saw Cain's descendants becoming more and more godless and sensual. They settled further and further up that mountain ridge where were the fallen spirits. Those spirits took possession of many of the women, ruled them completely, and taught them all sorts of seductive arts. Their children were very large. They possessed a quickness, an aptitude for everything, and they gave themselves up entirely to the wicked spirits as their instruments. And so arose on this mountain and spread far around, a wicked race which by violence and seduction sought to entangle Seth's posterity likewise in their own corrupt ways. Then God declared to Noe His intention to send the Deluge. During the building of the ark, Noe had to suffer terribly from those people.

There's mention of the fallen angels on the mountain (the Watchers), but also how they possessed the women to seduce the seed of Seth, much like is stated in Genesis 6:2:

The sons of God seeing the daughters of men, that they were fair, took to themselves wives of all which they chose.

But there's also the correlation of the possession of these women by the fallen spirits in Genesis 6:4:

For after the sons of God went in to the daughters of men, and they brought forth children, these are the mighty men of old, men of renown.

Now, "went in to" has the obvious meaning used elsewhere in Genesis of the sɛҳuąƖ act; but, given that these are spirits, one could see the DR English of "went in to" as meaning possession as well. And then there's the Latin of ingressi, which, as a feminine participle(?) of ingressus, means "entry, going in or embarking on, point of entry, steps".

And then, further, we come to the Hebrew, which is בּוֹא (bo), as in יָבֹ֜אוּ (yā·ḇō·’ū) which means "To come in, come, go in, go"; as a sort of movement, rather than the conjugal act, as evidenced how it is used elsewhere in Scripture: https://biblehub.com/hebrew/strongs_935.htm

Given that it appears to mean more that of a movement on the part of the sons of God (fallen angels, presumably), it does sound more like possession on the part of these spirits, with the conjugal act occurring between the other "sons of God" (Seth's progeny) and the possessed women to produce the Nephilim. As Anne-Catherine's vision relates.

So, what I'm seeing here is that "sons of God" is being used both in the sense of Job to mean angels, but also in the sense of the just men of that age, Seth's progeny.

It seems that Emmerich is confirming that angels/watchers did fall, which St Augustine couldn’t rationalize.  She agrees with Enoch, while St Augustine doesn’t.  

As far as genetics and reproduction goes, I also see an *apparent* contradiction between Emmerich/Enoch/Scripture and St Augustine.  The former imply that the angels did reproduce, because that’s the only way the giants came about.  While St Augustine is saying that the fallen angels used seed from men.  But St Augustine doesn’t explain how/why the fallen angels were able to create super-human giants from ordinary woman/man genes.  

It seems that St Augustine tries to downplay the fallen angel “father” theory because of the unexplainable lack of human matter but then creates the same problem with his fallen-angel-influence of normal human reproduction.  Either way, it seems to me, the fallen angels corrupted human matter and created the Giants.  Either they created/provided male genetic material or they corrupted/enhanced male genetic material.  Both situations are other-worldly, and supernatural events which are foreign to our concept of angels.