My take on Vega’s match-ups from the little experience I’ve had so far, mostly playing ranked matches against a diversity of opponents in terms of skill:
Unfavorable:
Ryu and Cammy
Even:
Bison, Chun-Li, Dhalsim, Karin
Favorable:
Rest of the cast
Biggest problem when fighting Ryu is that his fireballs stop your mid-range game. You can only punish them if you read them, Vega’s jump has the exact same duration as a Hadouken’s full animation. Therefore, if you want to play safe and get rid of the unsafe things, you just have to block those projectiles most of the times until you can either poke with st.MP/cr.MP, or mix your forward movement with shimmies and make him whiff something. Dashes are good as well, just make sure he’s not in a fireball mood. When you have meter, risk an occasional EX Roll. If he doesn’t jump or V-Reversal you, he gets carried all the way to the corner, which is nice.
His low normals have quick recovery, so you most likely won’t be able to whiff punish with claw st.HP, which sucks. Baiting DP’s is nice though, if you have a meter you can go for 330 damage + Okizeme, which is pretty neat.
Also, *** his jump arc is stupid lol. I can’t anti-air it with st.HK most of the times, and have to rely on either j.MK or Air-Throw.
It doesn’t mean you simply get rekt automatically, but you have to read way harder when you play this matchup.
As for Cammy, I feel she can just EX Dive Kick Vega all day, and once she’s in, her offense is above average. Your best bet for fighting her air approaches is to simply prevent her from jumping, by throwing repetitive long ranged pokes and an occasional st.HK. If she gets the air though, it seems like you can only try to clawless cr.HP her dives, use j.MK or try a read with an EX FBA.
Just like Ryu, I don’t find her too easy to whiff punish, but if you can get a good read, the round swings heavily in your favor.
Also, make sure you store a bit of your focus on neutral to punish those V-Skills or block long-ranged Spiral Arrows. Controlling stuff in the air is important, but she has some pesky approaches on the ground as well.