I've used Nix for 5 years now and use it heavily in production, and in my opinion, just do what works for you. If you try and use Nix 100% "correctly" then you'll end up like the countless other people who tried Nix and failed.

Especially for toying around in dev environments, be pragmatic and take advantage of its amazing strengths, but if distrobox lets you enjoy using NixOS and speed up your workflow, so be it.

Heck I'm spinning up some services in production just now and I'm reaching for Docker Compose as that's how the vendor officially supports deploying their software. Turns out NixOS can still bring some benefits to a Docker Compose workflow, deploying it via a systemd service, config managed in Nix, it's not as nice as building the service entirely in a Nix derivation and deploying it natively, but it's still better than without NixOS.