I've found NixOS is fantastic for evolving my environment. Update `configuration.nix` and then `sudo nixos-rebuild switch`. Done.

What kind of "tweaks" are you doing? You could use `nix-shell` to try out a new environment. If you like it the environment, you can make it declarative by creating a `shell.nix` file.

If you want to go further, you might make consider making a flake, but I would recommend reading https://nix.dev/concepts/flakes.html first.