Recent testing revealed that Arch Linux, Pop!_OS, and even Nobara Linux, which is maintained by a single developer, all outstripped Windows for the performance crown on Windows-native games. The testing was run at the high-end of quality settings, and Valve's Proton was used to run Windows games on Linux.
If my experience is any indicator, your GPU is fine :(. Any chance you’re using mixed display scalings? I’ve got an RTX 3050 eGPU for my Plasma/Wayland laptop, and for the most part it actually works fairly smoothly (albeit more slowly compared to windows), but if I try to run a game at a higher resolution than my monitor (used by Plasma for mixed scaling) I get constant flashing/frame shifting, but when I drop it down to the native 1080p it starts working again
As a side note, X and eGPUs do not play well together, but Wayland is literally plug and play after installing the drivers–I can even hot plug/unplug as long as nothing’s using the GPU!
I played around with scaling a bit, but removed the commands in my sway config afterwards. I do have different screen resolutions tho.