I don't know of anything about nvidia being "way behind", apart from wayland support. The only case I can think of the top of my head where the bad wayland support comes into play is if you have multiple monitors with different refresh rates. But maybe even that is not an issue anymore with new nvidia drivers. Maybe others can comment on it as I no longer have an nvidia card to check.

Use protondb to check whether your games play well on proton. It shows each commenter's system specs as well, so you can see if a game has issues on nvidia specifically.

https://www.protondb.com

One warning: don't try to install software, including the nvidia driver, as you would on windows. On linux, you don't go and download it from nvidia's website, you get it from your distro's package repositories, and you let it get updated automatically via your system updates. Depending on the distro you install, it might be as easy as checking a tickbox to automatically install "Additional drivers" or "Proprietary drivers" during installation.

EDIT: I assumed "way behind" to mean that nvidia is behind amd on linux. If you meant how much linux gaming is behind in general, that's another story. Linux does tend to lag behind in implementing newer features like newer DLSS versions. If you're worried about this, then perhaps you will get more information if you post a question about what specifically you care about.