@blood your link doesnt seem to work btw lol
but yeah it's not 2d guys. It's made the same way as all mainstream fighting games are nowadays, which is 2.5D. 3D models that play on a 2D plane (ie sf4, sf5, kof14, killer instinct, mvc3, mvci, GG xrd rev 2). GG xrd rev being the closest example as it's made by the same developers arcsystem works. As for the mirroring, i suspect that it's because it's easier than animating the model to turn completely around and then animating new animations for the other side of the body for the same moves. So the fact that it's actually 3d models allows them to do the dynamic angles more easily like when they do a dust launch (pardon my GG vocab) and angles for super attacks, as well as stages where the background can get destroyed (ie deflecting ki blasts into the background and it destroys the buildings).
An example off the top of my head i can think of is in KOF14, the character benimaru has an asymmetrical design, and you can see his actual model turn around instead of being mirrored, HOWEVER, in the same game a character named nelson is mirrored instead. Nelson has one bionic looking arm and his sprite is simply mirrored instead of animated to turn around like benimaru, which is weird and inconsistent but oh well lol.
I was hoping they would fix the kanji issue on goku, but it doesnt look like they will, which is too bad. Overall though, im really excited for this game, got to play it at the last evo tournament and it's awesome, january cant come soon enough!