Poor performance in all games with high-end PC

re: Lubuntu - There's a reason why I recommended Pop OS, because it's geared towards gaming and getting NVIDIA's driver mess to work properly, no need to invent with distros made for other purposes.
If Manjaro works out of the box with NVIDIA for you, I'd not recommend any Ubuntu based distro over it.

I have no idea what's wrong with your Windows setup then, just wanted to confirm whether it worked fine on different conditions

(You can also get better performance on Linux through further tweaks and game settings)