Difference between 2d and 3d games
2019-03-173D Games
On a fundamental level, 3d non weapon games want to be played close up, which means small pushback, stand/button blocking, weak lows, and lots of close range evasive options. (also reactable throws). it also impacts the camera style (zoom in when close range). In 3d games lots of damage will come from callouts (calling out an opponent tendency, via backdash/sidestep into whiff punishing, or blowing out strings by exploiting option selects or opponent's tendencies in string choices).
2D Games
Traditional 2d games want to use most of the fixed camera screen actively. At close range throws are strong because you don't get to stay there too long, most attacks have big pushback. And you'll get out of range after blocking 2 or 3 attacks, you also have more "+frames" attacks which make it so you don't change turn all the time, so you have to block more and you will get pushed out of close range all the time.
In 2d games characters will walk in and out much much faster (and also run/dash/jump/superjump/hop/hyperhop/shorthop/superdash etc.). In exchange of that vastly increased amount of movement options, you get more "movement restricting moves", lows are a lot stronger in 2d games, which make crouch block the usual default blocking stance, proximity block is a thing in a lot of case (you stop moving when your opponent is attacking in your global vicinity), in between other stuff that roots you on the ground. You also get full screen attacks (fireballs and dashing attacks). In 2d games lots of damage (past beginner level) will come by manipulating your opponent's attention and then surprise him with one of the many, many, many attack paths. It might be, hitting your opponent with a fireball while he was trying to tag you with a long range low attack, or a good old dash into button SFV style after your opponent just whiffed a heavy attack and is wary of a jump.
By the way
Obviously callouts and whiff punishing are a thing in 2d too, and attention manipulation is a thing in 3d too. I'm just giving out big tendencies but in reality it's all a continuum.
Another difference, 2d games are generally more "vortexy" than 3d games (depends on the game). 3d games have more complex wake-up systems, the down is meant to break the pace of the game to give the defendant space. In 2d games down are seen as an achievement for which you should get a reward (called okizeme), in that the attacker gets into an heavily advantageous situation. On a similar aspect, few 3d games have "stun" or "guard break", it's a pacing issue.
Keep in mind ~~~
SFV is a special mixture which is pretty "tekken-y" SF, in that attacks (and throws) have very small pushback, which makes frame data much more important than it used to be because you stay in close range much longer, in between a few other changes.
Shameless plug
I got a video for SFV ultra beginners. Put the subtitles for english. It has lots of stuff you probably already know but it probably has lots of stuff you don't know yet!