TLDR: ... I'm getting a comparable experience to NixOS, with all the usual pros a declarative environment brings and without having to put up with Nixlang.
Nixlang is so infuriatingly obtuse that I generally have to fire up Discord and bug the local Nix acolyte when something goes wrong. I've bounced Nixlang off of the LLM/AIs, but I have learned that if the AI doesn't give you the correct answer immediately for Nixlang then you need to stop; everything forward will be increasingly incorrect hallucinations.
I suspect LLM/AIs will hallucinate far, far less with the Scheme from Guix.