A 'Full profile" backup does indeed just zip up the entire Fx profile
including any/all files, directories and sub-directories. So if any extensions store their data within the profile folder, it does get backed up. If any cache and/or phishing database exists, they will be backed up unless the FEBE Options > How to backup > Ignore cache and phishing DB
A "Selective" backup, however, only packs the extensions into installable .xpi files - much like what gets installed from the Mozilla Add-ons site.
I have written a couple of extensions (OPIE
) that export extension preference data that can be imported into new installations.