Maybe etckeeper fits your use case? It’s specifically built for managing /etc files with version control systems. I can’t say much about it since I’ve never used it, though.

If you mean use both at the same time, you can! If you check out the website for Nix (or Guix, its Lispy cousin), instructions are provided for installing it alongside your current distro as an additional package manager for those who want to use it without reinstalling or using a vm.