As far as I know Atlas OS only supports Windows 10 (for now) I would say Windows 11 is significantly better from a security perspective so if your PC supports it use that instead. You are trusting a third party to apply the changes on your operating system, so I guess it’s up to you on how comfortable you are trusting Atlas OS or privacy.sexy. I would personally recommend reading through Microsofts documentation on group policy so that you can remove things that you don’t want, then you don’t have to trust a third party with editing your system.
According to their docs Atlas OS only removes: 
- Windows Defender
- Restore Points and System Reset
I also think you might run into issues with Anti-cheat because you have edited the system so heavily.