Or you could just use user.js and not have to change every setting manually each time you start from scratch.

Yes, Betterfox all the way in + few custom settings.

I am still in position where I need to put some small pipeline to automatically download latest + merge my stuff and deploy, but even if it's manual every month or two it's not too bad.

Did not know about 'user.js', thanks! I guess creating a document that lists all my overrides was the first step. Now I have to figure out how to create a user.js that works on Linux, Macos, Windows, and maybe Android?

Same file works everywhere. Just leave out the ones that are different on platforms:

- browser.download.dir

- browser.helperApps.neverAsk.saveToDisk

And instead of making a "google doc" a plaintext file would be better.