I've not used Guix but I don't think any distro has anything close to number of desirable available packages as arch--- so be prepared for that. My ventures into debian, suse and fedora were made quite annoying by having to work around the many missing packages. Including user-facing applications, dependencies and background programs. I never quite got down with distrobox, maybe that's the cure.

this chart on wikipedia gives the impression that Debian has more packages but that's not the way it feels when you are looking for something. Maybe they have a lot of dot matrix printer libraries from 1992 or something which bring the number up.

Arch includes a lot of not-at-all-free packages (which it is impossible to distinguish in pacman or other tool as far as I can find), orphaned, new packages that haven't yet made it into other repos, and packages where no attempt has been made to submit them to other repos.

On arch I have virtually never had to go outside the repos for packages. It's very hard to give up once you are used to it. (Even though it's better to use properly libre/free stuff and other benefits of a more curated approach like security, stability and quality.)