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Linux vs Windows tested in 10 games - Linux 17% faster on Average
(video.hardlimit.com)
This is a most excellent place for technology news and articles.
Nvidia is likely the problem, also you mentioned dual gpu, make sure your not on your iGPU
Edit: details.
I'm not on the iGPU. I use prime-run to run Steam, and all games properly detect the nVidia card. Also, I doubt the iGPU could run Hitman at max settings at 60FPS@1440p.