Nope it doesn't
Firefox
A place to discuss the news and latest developments on the open-source browser Firefox
Manually
What about extension settings? Is there a universal rule or is it per extension and up to them?
There is a ability, iirc for extensions to use your Mozilla Sync account for storing settings. However it´s up to each extension developr to include this.
Yes, turns out you need to manually enable in ublock and then manually export your rules yourself. Better than nothing, I guess.
You have to take care of your backup. Mozilla takes care about ai and translations.
To be honest I think it's better they don't sync these kind of things that are "hacky". Someone who breaks his Firefox and don't remember how should be able to make a fresh install to fix everything.