Being a 3D gamer gone 2D, i 100% understand.
The mixups in 2D games are different. Depends on the game, too, of course.
3S, SFII and SFIV and games like that which are about footsies, I can’t help with.
however, the newer games have mixups. Crossups are a form of mixing up, getting them to block wrong. Also, in some games, you can do instant overheads (or just plain overheads) which catch them if they’re blocking low. Some games have it so they can’t block certain moves (or at all) in the air. Get them to jump and nail them with that. And there’s always the throw/attack mixup.
The thing about some 2D games is that it’s a lot more combo focused, and a lot more situation oriented than 3D games. In Tekken, you launch and unless their back is turned, you do the combo. Walls make things change a little, but overall, its pretty easy to judge that. Same in 2D games, you have your basic B&B, but depending on situations and meter and such, different combos are better to use. Learning all those situational combos are what makes it so hard sometimes.
It really depends on what game you’re trying to learn. I play 2D games, but to me, the difference between SFIV and Arcana Heart 2 are so huge, that they’re not even on the same plane of fighters. Arcana is a combo based fighter (as is Melty Blood, Guilty Gear, etc) and SFIV is a footsies game (as is ST, 3S, etc), and they simply can’t be played the same. Some people can be good at both, of course, but other people can only play one type. I don’t even really understand SFIV, so I can’t explain it. But its definitely way easier to play a 3D game than a 2D game, imo. So be prepared for it to feel very uphill, but as people said, watch video’s, see what they’re doing and why they’re winning. Once you start to see that, you can begin to emulate.
allstyles - Same in 3D games, you have to know how far an opponents move is gonna go so you know if it’ll whiff or if you can punish it with a certain move, if so, what move. All depends on the recovery of the move and the reach and so on. You don’t need to know that stuff any less in 3D games, imo.