If I can stow all of my dotfiles, why would I use home-manager to handle them instead? In most cases it's just going to be harder to configure anything, and you also need to rebuild your home every time you want to update a config.

Yes, yes indeed. That's why my dotfiles are still in a git repo (don't get the point of stow), not in home-manager.

If you do in fact need home-manager's features for some of your dotfiles though, it can effectively act as a stow superset for the rest.

What benefits does it have over just using a shell script?

Declarative stateless configuration rather than imperative stateful configuration.

With a bash script, you'd have to meticulously craft together the i3config file using shell script syntax and remember to run that every time you change something. home-manager just does all of that for you with high-level data types and frameworks specifically made for that purpose.

that ties into another problem I've had when messing around with home-manager: the only source of options I found was mynixos. So to configure anything I had to first guess potential keywords to search for the option I'm interested in.

Yeah, it's not great. https://search.nixos.org/options? is really useful for NixOS.

You have to either use your browser's dumb search on https://nix-community.github.io/home-manager/options.xhtml or your pager's dumb search in man home-configuration.nix.

Can you give me some examples, what issues will I face running MX + nix that I wouldn't if I ran nixos?

All the issues which declarative immutable stateless system configuration solves such as atomic updates, configuration rollback in case you messed something up and trivial recovery. I'm sure I'm forgetting some since I'm so used to having them.

The main problem was getting started from 0, so I'm considering writing a post about it when I get a bit more comfortable. Trying to learn nix declarative package management from the nix manual is a bad idea, and almost all of the resources are on nixos. A quickstart guide with a few commands and examples would've had me up and running in 10 minutes instead of days.

Yeah, docs are a pain point. If you think that section is bad (I think so too), everyone will thank you for rewriting it. Feel free to shoot a PR to Nixpkgs and ping a few people from the docs team if you're motivated.

Yet I never see it mentioned, while even beginner threads are being spammed with nixos recommendations.

I don't get it either. NixOS is the best thing since sliced bread for a certain kind of person (experienced hacker who has felt the pain points which NixOS relieves) but I'd never recommend it to an inexperienced user in its current state.