#1
I currently have a Tiny Terror with an Orange PPC112 cabinet. Can't complain! For my needs it sounds awesome! However Ive been wondering: if I get another PPC112 or just a PPC212 cabinet, will my overall sound change? Will it sound louder? Also can I buy for example a Marshall cab and use it along my Orange cab? Thanks!
#2
If I were you I'd get a PPC 212 for a fuller sound.

You can use any guitar cab as long as the impedance is correct, brand doesn't matter. But if you're thinking of buying an MG cab, don't.
#5
It'll be quite a bit fuller sounding, a little bit louder, a lot more thumpy bass on tap if you want it.

If you buy a different cab or one with different speakers, the tone difference will almost certainly be noticeable and possibly quite significant. Same noise, different flavour.