I noticed a huge jump in 4bets going from 10nl to 20nl and it's definitely a scary new thing to me even being appropriately rolled for the new level. I play about 25% top hands and less based on position. I'm okay flatting, but I get punished on the flop because 99% of the time they'll bet and I'll give up unless I hit a top pair or draw then give up turn with nothing. Which is often and just depletes my roll so quickly.

If that’s your postflop strategy, you might want to reconsider moving up.

One thing that’s certainly superior to your current strategy is to never flat 4bets OOP and instead always shove or fold, given max 100BB stacks.

This is for cash by the way. What hands should I be playing to be in that position to shove? Let's say I have 9Ts mid position and 4 bet in to. Players unknown and Huds aren't allowed on the site.

Why did you 3bet T9s in the first place?

+1 Geez.....

The short answer is very few. It's opponent specific as well so it's hard to give you a default range. If you'r using a hud your opponents 4bet % can be used in part to determine your flatting range. Even without one you'll have a feel for how aggro they are post flop if your playing with them for a while.
The post flop difficulties your describing tend to further the argument that you shouldn't be flatting 4bets wide. With respect I doubt your good enough to get away from say AJ as TPTK post flop when your opponent has AK/AQ. I don't know what site your on but my experience of 4bets at 25nl on Stars is that they should generally be respected without player info to the contrary.