Earlier quoted context omitted.
Game changer! Now from my POV Firefox is the best desktop browser, period. No caveats.
Is there a good transition path for someone who uses a lot of Google products? In particular, I use Chrome across all my devices, and I depend on the ability to search my history/recent tabs/etc from anywhere. Will Firefox give me the same ability? Is the transition literally just: Install Firefox everywhere and start using it instead?
Yes.
> transition literally just: Install Firefox everywhere and start using it instead?
Almost. You will have to create a firefox account and export/import your bookmarks. That's it.