Linux

If I'm being completely honest, it sounds like you hit a problem and then just kinda gave up (I'm not trying to sound mean or anything - please don't take it that way).

If I were in that situation I would probably drop to a terminal (ex. CTRL+ALT+3) and try to find what failed (journalctl). Especially if the screen just stayed black I would probably wonder what packages I just updated. I'm not going to remember, but it's probably something graphical. Maybe I installed nvidia dkms packages and I have a mismatch or I decided to try out a different login manager and it happens to not support Wayland or something. Snapshots would be my last resort, not my first.

As far as NixOS, I love it. Its incredibly stable and the declarative language is really handy to write in. I'm not aware of any graphical store though (outside of maybe some github project). Its declarative meaning you write the configuration.nix file and import any secondary files into the config. And packages are installed declaratively:

environment.systemPackages = with pkgs; [
    pkgs.gnome-tweaks
    pkgs.gnome-control-center
    pkgs.gnome-terminal
}

I would say if you are wanting GUI that NixOS is probably not a great choice. I mean just to get installed package version, you're going to have to do a one-liner (mine for example):

#!/bin/bash 
find /run/current-system/sw/bin/ -type l -exec readlink {} \; | sed -E 's|[^-]+-([^/]+)/.*|\1|g' | sort -ui