Most of the games work. The only problem linux has right now is anticheat in some games. But you cann look at https://www.protondb.com/ to check which games work.

It depends on the type of game you play. Most problems occur with online games, the vast majority of single player games, even AAA, works on Linux, notably with Steam.

As I said in another thread, I do not check compatibility anymore beforehand. I install and select the newest glorious eggroll proton in steam and it works. Granted, I play only indie games, so if you play competitive with anticheat I would stay on windows to be safe and avoid the hassle or suspended account.

In regards to performance I don't know if I am missing out.

Edit: https://programming.dev/comment/1457683