Yep. I did this about a year ago. You have to create a Mozilla account (if you haven't already) in order to sync your tabs and history across devices, but that should be a given.
I find the Firefox sync a bit clunky compared to Chromes though. I think Chrome sends udpates to Google on each change whereas Firefox polls and updates on a schedule which means sometimes if you put a device to sleep (or if you're on iOS and the app gets suspended) your history and tab state won't be propagated and it'll be missing on your other devices which can be frustrating when you're away from those devices.
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.
> Passwords can now be imported from Chrome on macOS in addition to existing support for Windows
Yes, each (bookmarks, history, passwords, tabs ) can be turned on or off per device basis.
“How Firefox Sync keeps your data safe even if TLS fails” https://support.mozilla.org/en-US/kb/how-firefox-sync-keeps-...