Your tall plant is Portulacaria afra. Some folks call it a dwarf jade, but it is not really a jade (Crassula ovata) at all. It can grow large, but also can be a very attractive plant. It is sometimes used in bonsai, so yes, you can prune it.

I would remove this plant and pot it up separately. That's my personal opinion, but it obviously grows at a different rate than the other plants in your mixed container.

Ahhh never thought of that!! I will do just that. It would be attractive looking since it had the nice woodsy bonsai looking stem. Thanks!!

good advise from Crenda.