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I think at 5 miles out, 23 feet would still be too small to notice viewed from 5 ft off the ground, of the curve is already subtle at 1 million feet off the ground.
 There should be a drop of 8 inches per mile at 6 feet. Which means the curve should be noticeable at certain distances, but, it actually isn't, as there are now cameras that allow you to see much farther than the purported curvature.

The distance you would have to be away from 2 buildings 20 miles apart would make them too small and short to see any tilt. Maybe if a powerful spotlight was attached to each building on a hazy night, pointed up and perfectly aligned to the buildings, you might be able to see from far away how much the buildings lean apart if any.
There's several experiments where lasers were used at a distance which should have hid them behind a curve, but they hit their target without any issue. They're on bitchute, which I cannot access at the moment. These tests, and those like it, are explained away as a trick of refraction around the curvature, which is nonsense.

This flat earth stuff is new to me, so I have a mind to argue it.

Have flat earthers explained the satellites in the sky I can see at night?
Look into NASA's helium budget, it's outrageous. Some purport that satellites we see are tethered to high-altitude balloons. It's not a definitive explanation, unfortunately.

Either way, one's belief flat or round does not affect their salvation as far as I know.
No, not at all. But we still have God-given reason to figure out just what we live on without Freemasons at NASA obfuscating that.

I think at 5 miles out, 23 feet would still be too small to notice viewed from 5 ft off the ground, of the curve is already subtle at 1 million feet off the ground.

The distance you would have to be away from 2 buildings 20 miles apart would make them too small and short to see any tilt. Maybe if a powerful spotlight was attached to each building on a hazy night, pointed up and perfectly aligned to the buildings, you might be able to see from far away how much the buildings lean apart if any.

This flat earth stuff is new to me, so I have a mind to argue it.

Have flat earthers explained the satellites in the sky I can see at night?

Either way, one's belief flat or round does not affect their salvation as far as I know.

In your Vegas skyline image, 10 ft is around the size of 1 or maybe even half a pixel on my screen, or the height of one story of the gold buildings which have easy to see windows. Will you really notice 10ft comparing them from so far away when they may not even be built on the same altitude of ground level?

That chicago picture looks to be taken from roughly the same distance, so it also is only about 4 miles wide. But lets imagine a 25 mile separation between buildings. What would it look like? I have a round plastic pretzel bottle/container beside me that is about 6" in diameter I can use to scale the earth down to, so I can better visualize things. With the earth having a supposed 24,901 mile circuмference, 25 miles out of 24,901 makes the skyline 0.001 of the distance around the earth. To scale it down to my container: .001 x 18.84" = 0.01884, which is about 1/64" or the thickness of my thumbnail. If I try to line up two rulers like skyscrapers on the side of my container only 1/64" apart, while trying to make them straight up and down relative to the container, there is a small but very obvious leaning apart of the rulers. A flat earth win?

Not yet. My rulers are not scaled down to building size, right now they would be stretched out like halfway to the moon (not really, but you get my point). So, how big would the buildings look on my container? Assuming they are 50 stories tall, 500ft, lets get their size proportion relative to this 25 mile gap between them. 25 miles is 132,000ft. 500/132,000 = 0.00378. So, I can't imagine what the size of my buildings would look like on my round container because they are smaller than a spec of dust if 25 miles is the same as the thickness of a fingernail.

Lets look at a ruler and and say 25 miles is 25 centimeters. 0.00378 x 25 = .0946, lets round it up to 0.1. So each 500ft tall building is only 1 millimeter tall on the ruler on this scaled down 25 mile skyline. To have the scaled down curve of the earth, the ruler would need the middle raised by a half millimeter. Hardly noticeable. If you have a hard time telling how different the each 1mm tall building is leaning at 25mm or cm apart, it would be quite hard to tell how far the buildings are leaning let alone just seeing them from so far away. The advantage of the ruler perspective is that you can get very close and still see the scaled down buildings, and the scaled down curve of the ground, but in real life you can't get that close of a look.

The reason why you don't notice the curve looking side to side, assuming you can only see 5 miles, looking side to side you now see 10 miles, but in any given direction you are only seeing 5 miles. Once you look the other way, you are still only seeing 5 miles out, but in a different direction. It's like you perspective gets reset each time you change your view. I think this is why even panorama camera images look so flat.

Given how subtle the curve of a ball earth is, I think it is not a good proof one way or the other due to the difficulty of proving it. It seems that to know for sure, one would have to fly into space really far to see for them self.

This doesn't bother me, I only care about truth.