It's recommended you do a completely clean install of Windows.
If you are on more modern hardware, it is highly recommended to go with Windows 11. Features are better, hardware scheduling is better and you'll be on a better supported platform. Do NOT use Windows 11, if you're on an unsupported system. Many anti-cheats require TPM and Secure Boot nowadays.
It is recommended to use an optimized Windows installation like ReviOS, which comes in both Windows 10 and 11 variants. If you don't care about anti-cheat and just need the utmost performance, you can try AtlasOS. Older systems benefit from such an optimized OS significantly more.