Currently, I’m on a Guix System, and I must say, using Nix with it, or vice-versa, is a terrible idea because of one simple reason: contamination of environment variables: PATH, LD_PRELOAD and LD_LIBRARY_PATH, just to name a few. Most of my Flakes are useless on the Guix System, and I can imagine the same for Guix expressions on NixOS.