The repositories already contain pre-compiled packages. To install them, just add the repository before the Arch repos, and then simply reinstall the packages to install their optimised versions.
It's the same principle. Both CachyOS and ALHP are reasonably popular, and all their stuff is open for anyone to review - Cachy's stuff is all on Github and ALHP is on SomeGit.
never heard of them. I need to research a bit more until I activate what is basically another "dangerous" non-maintainer repository. Thank you a lot for your links and explanations!