Changing depths doesn't have to change the balance really. If generation used more relative vs. specific numbers, that would pretty much solve the problem.
Even so I'm sure they are looking at ore balance as they tweak things. Also, anyone making custom datapacks/etc. should take that into consideration as well.
I should also make a slight update to my post:
Unfortunately it seems that this new snapshot is bugged. I haven't tested actual full custom dimensions, but at least the overworld ignores setting the max height over 320, and crashes with min_y beyond -64. So, for 21w_06a at least, it looks like larger worlds are a no go. So, you can either have really big worlds ( by using one of the previous snapshots ), or new cave generation/etc. Not both.
Hopefully they fix that up to allow much higher worlds again, and ideally they add a simple world setting in game to change the height / Min_y on creation.