I think there's a big difference between a 20bb stack and a 30bb stack, with 20bb yes you can pretty easily 3bet/fold a lot. Once you have 30bb it becomes a bit trickier. With 40bb you have a bit more maneuverability, but I still like min raising all my opens or very close (2.3x) to keep options more viable post flop. For me it is 30bbs, which is why the 30bb cap games on FT can be tough until you get the hang of what you should be doing with a stack that size.

One more thought is that with a shorter stack you have less variance in the situations you're in because effective stack sizes are usually for what you have left or slightly less, whereas if you have 40bb you're playing against people with 10bb, 15bb, 20bb, 30bb, 40bb, etc and there are differences in what you should be doing based on what the other stack sizes are.