https://github.com/arkenfox/user.js
Contrary to what LibreWolf claims you do have to sacrifice usability though, including WebGL, DRM, Firefox Sync, autofill, history, and the occasional breakage. With arkenfox there is also letterboxing, and even more breakage. If you set uBlock Origin to the recommended medium mode you usually still have to whitelist third-party scripts to make websites work.
These considerations rely __HEAVILY__ on your browsing habits.
I've been using librewolf for quite a bit and only two sites required webgl (to use them I simply had to toggle webgl.disabled in about:config which I find acceptable since I've never had the need to use them after that occasion).
I do not visit sites that use DRM (I used to use Netflix but their service sucks so much I'd rather pirate stuff)
There are extensions to sync browser data with e2e encryption.
I find password managers are more usable than the builtin manager of the browser.
History has always been an annoyance more than a feature and I'd disable it either way
This is just my opinion, try it yourself for a couple of months and see by yourself if it's something you'd consider daily driving.
Replacing a core functionality with an extension is not obviously beneficial either when it comes to privacy or security.
I now prefer a browser without any history and cache and make heavily use of the bookmarks and adding exceptions for specific sites that should keep cockies between sessions. I can use the address bar to quickly find a site that i have bookmarked without having the results cluttered by search suggestions and years of history.
My general assumption is that, if I let Firefox autofill my address, it will insert portions of my address into various fields at random, biased somewhat but not very strongly toward getting them in the right place.