The main source of information about installing and using NixOS is the NixOS manual. Inside a NixOS system, you can read the manual by running the command nixos-help, and you can see the list of configuration options by running man configuration.nix. You can also search the list of options online.
The Nix Pills are to convince you to give Nix a try, and to complement the explanations from the more formal documents, in short digestable pieces.
If you think you’ve found a bug, please report it in the Nixpkgs issue tracker (please use the label 6.topic: nixos).