Your observations are not correct.
a) You can install any add-on that you wish on the unbranded Mozilla browser
just like you can on Firefox so you can get the same functionality from both.
If you want a browser based on the latest version of Firefox you can install
the Icecat browser by typing this in the terminal:
sudo add-apt-repository ppa:gnuzilla-team/ppa
sudo aptitude update
sudo aptitude install icecat
(I prefer using aptitude but you can replace it by apt-get if you wish).
You can also install language packs for Icecat. Just type this in the
terminal
apt-cache search icecat
And then install the files you wish, e.g.
sudo aptitude install icecat-ro for Romanian support.
b) If you install Ubuntu you will also install a non-free Linux kernel which
supports hardware that is not supported by free drivers. Ubuntu also
recommends installing non-free drivers as well if they are available.
c) Firefox doesn't install non-free add-ons but it does recommend them (e.g.
Adobe Flash) and it doesn't separate the free and non-free add-ons. Also, the
artwork is not released under a free license.
