My Steam Deck also runs NixOS.
Because this way I can much more comfortably configure it, plus everything game related I automated through nix for my Desktop (e.g. mod installs, reShade config,...) immediately and without any extra steps also applies to the Steam Deck.
Yep, exactly.
To be fair, if you use Debian, Arch, Fedora,... long enough, you also know how to tweak your machine for every purpose. In Nix, it's just somewhat of a self-fulfilling prophecy, because you have to know how to tweak your system to achieve.... anything, and then it's the same tweaking mechanics for every other purpose as well.