It seems to swap textures way more often so high-res textures on frames and weapons get a little blurry if you swing the camera around, but that's absolutely bearable, haha
So after a little more time with Warframe on Linux it's almost indiscernible from playing on Windows
Textures tream a little slower and there can stuttering in new areas, once, as you build up a shader cache but after that it's just 60fps maxed
Couldn't be more pleased with it, and this isn't even Steam Proton supported yet
the tip of my Tiberon exploded like elmer fudd's fucking shotgun