Un leones viviendo en Castilla
If you want full system control and a rolling distribution with a good security setup, stay with openSUSE Tumbleweed. Immutable distributions like SilverBlue, Aeon,…are not recommended for everyone, only for those who don’t want to administer their system and who have good hardware and a good internet connection.
You can install Firefox from Mozilla’s own repository. It is a luxury to have in Debian a Mozilla repository to install Firefox.