During my use of nixos, I have been exposed to the dconf system to a much greater degree than I did on arch (in order to make a configuration declarative, I have had to interact with dconf so that nix writes specific keys into it whenever I build a new nix system). Is there a good place to learn more about dconf, and how it works with schemas? I have exposure to schemas through extension development as well and would simply like to know how the gnome-shell uses them in a general sense.
Schemas are part of GSettings; dconf is one of various GSettings backend, which implements an efficient key/value storage. In general, you should entirely ignore dconf, and consider it as an implementation detail.
The documentation for the GSettings API also contains details on how schemas work.