I confess confusion about what you mean by "sunken raised bed", and a mov[able] "raised bed"; such things strike me as nonsensical, and seemed not to be part of your original description [*].

"Sunken raised bed" --- probably not the best way to describe it.  A trench dug in the ground, about 9" deep, 3' wide and 6' long.  My son commented that it looked like I'd dug a shallow grave!  I lined the bottom of the trench with plastic scavenged from bags of potting soil, logo side down, white unprinted side up, slits cut in the plastic before I laid it, to allow some water to percolate through and go on down into the sand, yet retaining maybe 80% of the water.  Then I put down layers of sand, potting soil, lime, more potting soil, and fertilizer --- kind of like a thin layered cake --- with potting soil, and then the native sandy soil, on top.  So it's like a huge planter whose bottom is thin plastic baggage and whose sides are bare sandy soil.

"Movable raised bed" --- Patio Pickers brand, basically the same thing, if not the same thing, as this:

https://www.lowes.com/pd/EMSCO-GROUP-20-in-W-x-24-in-L-x-10-in-H-Earth-Brown-Resin-Raised-Garden-Bed/3341626



I did not bother with putting the plastic sheet (included) over the soil.  It is free to the air.  They recommend no more than three tomato plants --- I took a walk on the wild side, and planted four.

Google Back-to-Eden gardening. The secret weapon for crappy soil of any kind: MULCH and lots of it!

Find a way to get free mulch. There is a service "Chipdrop" which will drop off a load FREE as long as you live in one of their popular areas. I've been on the list for a year and still no mulch from them. However, a few tree-trimming contractors working with a local electric company have dropped off about 15 dump truck loads of mulch for me, so I'm set now. I even sold my mid-level ($1000) chipper since I don't have time to use it anymore anyhow.

Even a decent personal wood chipper can't compete with dump truck loads of mulch.

If I had it do over again (i.e., if I woke up tomorrow and found myself 24 years old and living in the city again), I would have made a SMALLER garden completely covered with plenty of hand-made (break a bunch of sticks by hand) and/or bags of mulch from the store (4 for $10 at a big box stores like Lowe's on sale). Mulch really is the holy grail of gardening. I would also bury larger sticks and logs in the ground for hugelkultur. Permaculture is also "where it's at" but it's not distinct from using mulch -- more like using mulch is PART of the broader technique called Permaculture.

I tested my first Back to Eden garden -- the shovel goes down into the ground like it's made of soft ice cream. This was hard clay soil, very poor, with no organic matter and wouldn't grow anything before. After just ONE YEAR not only is there a layer of rich compost, but even the original soil has been redeemed/broken down into usable soil!

Can't wait to see what I'll be able to do with this new garden --

Google Back-to-Eden gardening. The secret weapon for crappy soil of any kind: MULCH and lots of it!

Find a way to get free mulch. There is a service "Chipdrop" which will drop off a load FREE as long as you live in one of their popular areas. I've been on the list for a year and still no mulch from them. However, a few tree-trimming contractors working with a local electric company have dropped off about 15 dump truck loads of mulch for me, so I'm set now. I even sold my mid-level ($1000) chipper since I don't have time to use it anymore anyhow.

Even a decent personal wood chipper can't compete with dump truck loads of mulch.

If I had it do over again (i.e., if I woke up tomorrow and found myself 24 years old and living in the city again), I would have made a SMALLER garden completely covered with plenty of hand-made (break a bunch of sticks by hand) and/or bags of mulch from the store (4 for $10 at a big box stores like Lowe's on sale). Mulch really is the holy grail of gardening. I would also bury larger sticks and logs in the ground for hugelkultur. Permaculture is also "where it's at" but it's not distinct from using mulch -- more like using mulch is PART of the broader technique called Permaculture.

I tested my first Back to Eden garden -- the shovel goes down into the ground like it's made of soft ice cream. This was hard clay soil, very poor, with no organic matter and wouldn't grow anything before. After just ONE YEAR not only is there a layer of rich compost, but even the original soil has been redeemed/broken down into usable soil!

Can't wait to see what I'll be able to do with this new garden --

All very good and potentially useful information.  I had never heard of Huegelkultur before.  Makes sense.  My yard is so small as to border on being a joke.  Many people have larger driveways.  These are zero-lot-line patio homes with the left wall being plain brick, no windows --- maximum privacy in minimum space.  Many of my neighbors have small in-ground pools and have basically sacrificed their entire yard to them.  I wouldn't do something like that.  I want a yard, no matter how small.  I would get major blowback from my family if I would dig up the whole yard for fruit and vegetable gardening --- they like a pretty lawn to look at.  They squawked enough about the "shallow grave" I made.  So I do what I can.  I am teaching myself basic gardening and expect to learn from my mistakes --- and I will make mistakes --- as well as things I can't do anything about, such as blight, temperature extremes, and so on.

We're running out of time. Act fast.