Yep, I use Arch Wiki as a starting point even for NixOS issues, when they're not strictly Nix-specific. Before then, Gentoo wiki was the go-to, but Arch Wiki has surpassed it by this point.
I also think that the AUR is a great source of information too, since PKGBUILDs are really easy to understand and useful for determining how a program can be built and packaged, and you can go and use this to make other kinds of packages for a given program.