I don’t have a gaming PC or anything, I just have a laptop, so ymmv, but performance in Linux, even of Proton games, is noticeably far better for me. Things are faster, I can crank the graphics settings up higher without lag, and my fan spins less angrily. Linux is just generally less resource-intensive than Windows by a very wide margin, so I think it leaves more for the game? Idk. All I know is it works better.
I’m sorry but the majority of people absolutely do not use more than one display.