Okay, after reviewing the footage tons of times and looking over the way Tekken works. I have come to the following conclusions about Kazuya.
Moveset Stuff
-Devils Form is Purely Aesthetic. Seeing as of all ~30 moves we’ve seen, there is not a single example of overlapping Devil and Regular moves. As well, all Devil moves have a big impact or make use of the added abilities (ie Smashes, Wings for Double Jump and Up Special, Lazar beam for Neutral Special)
-Tekken Rage is a powerup Kazuya gets after reaching a certain percent. It at least gives access to a one use per stock hyper move which I think is called Heavens Door. And if it works the same as Tekken it should boost his attack.
-Kazuya does NOT have punch and kick buttons, as he has a full list of specials (A Min Min style Jump for Up B, Lazer Beam for Neutral Special, A Side B burst option that crumples opponents (seen at 1:25), and I think if he uses Down Special on Ground he crouches (more on that in a sec), if used in the air he instead uses Devils Scissors.)
-Kazuya has a crouch mechanic giving him a small list of moves to play around with. And may be the only character in the game with an actually useful wavedash.
-Kazuya has a Back Tilt and Diagonal Inputs. This allows for the crazy amount of moves we’ve seen.
-Kazuya’s combo attacks likely stem from inputs that are continually built upon. I guess they are standard fighting game inputs that need timed presses to keep going.
-Unlike Terry and Ryu, Kazuya can NOT cancel any attacks into others. They must be organically built to lead into each other.
- Like Ryu and Terry, his jump isn’t very useful. Though thankfully Up Special (Seen at 1:29) looks good for recovery.
-Electric Wind God Fist is missing so far. Though if I had to guess it’s a secret just like it was in earlier Tekken games till 7.
All of this makes me 100% sure that Kazuya is the most complex character in the game. By a HUGE margin.
Other Stuff
-The Tekken Announcer does seem to voice Kazuya’s victory screen. You probably already know this, but I spent so long hearing it I felt the need to bring it up. It is possible they also voice his CSS.
-Kazuya’s full list of Alts has not been shown off. If I may, there is a small chance Jin is an alt the team has saved for a surprise. Though he is more than likely a mii and/or spirit.
This took hours of work. I am confident that I maybe have this right.