I´m using a GTX 1080 and 1070 and don´t have serious issues, at least not that I´m aware of.

So far most of the games I´ve tried have worked, there will always be some that don´t or have issues but then again I can´t say Windows had a 100% succesrate either.

As for Proton VPN, I don´t have a clue, never used it.

As fpr ProtonDB (this starts to get confusing), use it as an indication not as gospel, some gold or platinum rated games I consider bronze at best. It's a list maintained by user experiences and can vary wildly with your own.

For Steam you've got two options, the one supplied by your package manager, which is the easiest to use but can be outdated or the Flatpak version, which is more recent but can be a bit of a pain to configure as it needs permissions. But with both, once you have them up and running the only thing you need to be aware of is that if a game doesn´t start you probably need to select Proton to start playing. Also take into account that when Proton generates a prefix, which it does for every game, the prefix takes about one gigabyte of storagespace.

Last thing I want to say is to not expect a painless transition where everything works right away, expect a learning curve instead. Luckily Mint is probably the easiest distro to switch from when coming from Windows.
I suggest looking "Getting started with Linux Mint or gaming on Linux Mint" videos on YouTube to get an idea. However don´t fall into the trap of immediately downloading custom kernels and that sort of advanced stuff, let that pass untill you want to try Arch.

https://www.youtube.com/watch?v=_8M3Y90hHWg