Actually, no... The VFs can't transform, it's a bit disappointing. The Konig Monster, however, can transform between all three forms. As for additional skills, you'll unlock more of the "TMS" ones as you play through the game, there's 6 total I think.
The main way to get skills is buying units from the same series. For example, Nirvash can equip TheEND's dual blades, and TheEND can equip Nirvashe's boomerangs. The Code Geass units share many guns and melee weapons. The Lagrange units can use each others' weapons and shields... The TMS units are universal, though, almost any unit from any series can equip them.