Concerning UES, there is a mechanic called Ki charge where the characters amp themselves to deal more damage and have counter hit mechanic. This is canoncially a thing because Heihachi used Ki charge in response to True Devil Kazuya's transformation. And this isn't exclusive to Heihachi since everyone channels their ki before using their unblockeable Move.
So yes. They use Ki even if its poorly mentioned.
(Also Kazuya realised Lars was his brother based on the similarities of their lightning ki)
Edit: You can customize Ki and Aura since Tekken 6 and
the same auras are shown here
So BlackDarkness is right on that one.