A set of digestable preferences lists to enhance Firefox. Updated every stable release. Just comb through the lists and add desired preferences to your user.js. Most of the preferences work with a simple copy+paste. I've tried to note where user manipulation may be needed.

Four categories:

FastFox: increase Firefox's browsing speed immensely.
CleanFox: removes Pocket and form autofill. Download preferences. Unclutters about:newtab.
PeskyFox: dark mode. Disable warnings. Blocks notification by default. Prevent Firefox from randomly going offline.
SecureFox: removes Telemetry, Google Safe Browsing, Geolocation, search engine suggestions in URL bar, and various security enhancements — all without breaking webpages by default!

Credit: Hours spent reviewing ghacks user.js, random websites and blogs, and keeping up with Mozilla updates.