One problem to take into account going forward:
Upon including (in the same guide) NixOS & al. you branch off the general Nix use case.
This makes the documentation unsuitable for a subset of the current audience.
An alternative would be to make separate guides on NixOS, home-manager from first principles, and thereby marking the different target use cases.
NixOps is a bit of a special case and there isn’t really a consensus about it’s design choices and target use cases as evidenced by the emergence of: morph, krops, colmena, deploy-rs, nixus, terraform-nixos, etc.
I’d personally say about nixops: maybe it’s eating up the world a little too much. But on the bright side, I feel the first principle of interoperability with other ecosystems is raising in the Nix ecosystem. 