Gaming on Linux is fine these days. Surely not a blocker for switching for the most part (except for some edge cases like some multiplayer games that depend on some weird anti-cheats).
I've made quite other experiences with my setup. I'm not that experienced but with my Ubuntu and i3 setup with the standard drivers from Nvidia I couldn't get playonlinux or wine running. I can't exactly tell what the problem in the end was, but it definitely is not as easy as on Windows or even Mac imo.
I surely won't recommend Nvidia for anything Linux these days. Get a decent AMD card. That said, Nvidia should work with Wine too. Most problems with Wine are caused by missing dependencies, like 32-bit libraries that are often needed for 32-bit games naturally.
I wouldn't call them fine if you consider general progress of the Linux desktop. Their integration with the whole stack is simply broken, due to Nvidia refusing to upstream their drivers. It's the reason they for years couldn't support PRIME (Optimus) and Wayland use cases, and despite their very slow efforts to address that, a lot of it is still broken for their blob (like XWayland use case).
Basically, if you care about the progress of the Linux desktop, don't use Nvidia, since it's only holding it back.
Steam with proton did work for some games but not with i3 only with the default Ubuntu window manager, I'm not familiar enough with this stuff to really tell where the problems are but I'll try Lutris, thanks!
I still cannot get nVidia driver to offer subset of native resolution. Eg. My display is 2880x1800, but I wish to game in 1440x900 or similar. Not a problem for other OS’s, but nVidia Linux driver doesn’t allow this.
Idk about nVidia since they insist on being a special snowflake in the Linux graphics ecosystem but for everything else you can add arbitrary display modes with xrandr and and then either let your display do the upscaling (might not support all resolutions) or configure your GPU to do it.
Most displays also just advertise a number of smaller resolutions - does yours not do that?