Comment by aidenn0

I think there probably actually isn't one "correct" way.

Anything that is best configured with a nixos module should probably be in your system configuration, but beyond that there are probably a lot more than 5 different ways and they have their advantages and disadvantages.

What I settled on was a per-user declarative setup (first with "nix-env -r", now with "nix profile"). Then I use nix shells to run software for one-offs. If I find I am running the same software from a nix shell a lot, I toss it in my declarative file.

Plenty of people hate this setup, and do something completely different (e.g. imperative managing of profiles, or using home-manager, or a dozen direnv setups). I don't necessarily think any of them are wrong, but they are not for me for various reasons.