Nix-OS is an odd beast, it is very, very different from any other Linux based OS I have used.
This is both good and bad
The Nix-OS install then interprets this and installs/updates/recreates itself using a single command nixos-rebuild switch ( add –upgrade to upgrade)
The biggest benefit to this is you can use this file across multiple different PCs & Laptops if it works on one, with minor tweaks it will reproduce the same install on others
The biggest downside to this is that the 'normal' way of configuring personalising your Linux installation does not always work, and you must learn to manipulate the configuration.nix file for the configuration you want to remain between updates and upgrades, and this means relearning a lot of basics.
I an still unsure of I like this, however it seems to work well and so far after a couple of months I am still using it
I may eventually move back to using Debian or Arch Linux as they are (imo) much simpler to configure and use