in FF afaict you can only use one at a time and you have to choose at launch
That said, do try multi-account containers, unless you really rely on extensions and theme being different per profile - they're great: https://addons.mozilla.org/en-US/firefox/addon/multi-account...
My only concern now is with using multiple devices. Do I just sign into to both profiles on each device? I only worry because there was a big snafu that occurred with their password manager that synced nothing and everything disappeared. (I no longer trust google with that stuff).
Firefox profiles are similar to Chrome's. But the container tabs that people are talking about in this thread are better than Chrome profiles. They're per tab, and last I checked they only separate out cookies and local storage.