FòrumCAT

You have to setup a Nix service and do some symlink-ing

https://guix.gnu.org/manual/en/html_node/Miscellaneous-Services.html

personally I like Arch first and foremost because I can (and do) have a local repo by rsyncing a rotation of mirrors couple of times a week.

Are these mirrors for prebuilt packages? If not, you should be able to pull from other channels, create your own channel and include all your packages while building them locally.

Also, welcome to Guix System Distribution, I hope you stick around

Let's say I'm working on a project that requires Go, Node, maybe some C library, and GNU Make. Seems like I would be able to use guix shell for this, right? Great.

Iirc guix shell is for one off package or programs you want to test, say you want to quickly format a drive to exfat or so, when you exit the sub-shell, the installed packages are discarded

guix shell containers would work best for your scenario but I have little experience with them