its better to install firejail + firetools by defaults. as hexchat,thunderbird,vlc has their built-in profiles coming with firejail to work with seccom. so these going to be by default secure + maintained by them.
rest of whonix components like TBB or …etc we can wait until the maintainer will show up. but for the rest i dont see a reason to stay back without installing it.
Note: firejail + firetools installed from the official Debian repo.