I think the large majority of gamers are GPU bound these days, and I'm suspicious that there's much you can tweak in the OS that improves GPU performance. Maybe I'm wrong and improving system latency helps.
I feel like GPU frames cost like 3x CPU frames these days.
It's obvious when you play games on a laptop with integrated graphics. You can tweak every in-game setting to the bare minimum and/or try to stop every service that's running outside of the game, and none of it makes a significant difference, because the core bottleneck is that there isn't a dedicated GPU.
The other big bottleneck that existed 10+ years ago is that people still used spinning hard disks. Now we almost all have SSDs, a big chunk of load time and source of slowdowns due to background processes is gone.
I feel like GPU frames cost like 3x CPU frames these days.