Thanks for the comprehensive write-up. It convinced me to migrate back to Firefox.
I was on Firefox (8 years ago), moved to Chrome (I liked the non-admin/transparent update feature and Websites didn't break like they did with ff), then moved to brave (basically chrome + more privacy), and now I'll go back the Firefox (I hope I won't encounter too many non-FF websites)
I expect to have some website compatibility issues with Firefox/librewolf, as it does have a 3% share of the global browser market - so, website development energy is focused on the chrome/safari experience. However, 8+ years ago I felt I needed to use chrome at least every other day to view certain websites - it was frustrating.
I'm hoping (and willing to try it out) to see if this has improved.
If you want to non ff sites to work on ff you can just spoof tour user agent. 90% of non ff sites actually work. Some use web usb and bluetooth stuff that doesnt work on ff.