Since it was asked, here are my thoughts/analysis:
Outside of 33B combos, I tentatively want to say that A+B is only generally going to be useful for its TJ properties against slow, ranged lows - or if you want a decent TJ punisher when you think your opponent is going to 2A/2K you while at disadvantage. The move TJ's late. A+B is an i25 move that has TJ properties starting on the 17th frame and lasting all the way until the impact frame.
A+B is really unsafe if the first hit gets blocked and the second hit whiffs. When spaced properly, or when your opponent is just somehow on the proper axis so that the second hit gets blocked though, then the move becomes safe and it force crouches your opponent as well (see the frame data thread for the difference in safety at close vs. max range). Also, it is sometimes possible for the first part to hit but have the second part whiff because your opponent is off-axis or something even though the move is technically a natural combo.
You get guarantees if the second hit of A+B lands and knocks your opponent down. 3B is probably the safest guarantee to not screw up somehow (plus it was a combo back in the SC2 days so it stuck with me); however, there is one potentially very annoying tech trap option as well. Either ways, your basic guaranteed options after A+B knockdown are:
3B
236B
1K
1B
2K
If you are looking to tech trap after the A+B knockdown instead of your guarantees (with the potential of a RO on both options if they tech), then you get two choices:
1A
4BB:A
4BB:A will catch tech in all directions, but it will whiff against grounded and rollers (there might be character specific exceptions to the grounded/roller thing - but the move definitely whiffs against Cass). Also, normally, A+B grounds face down; however, if you somehow ground them face up (such as hitting them with A+B when they are back turned) then 4BB:A becomes guaranteed as it will give them a minor ground re-bounce which 4BB:A can then pickup.
1A deserve special mention because the situation it generates is somewhat unique and can be really annoying if your opponent does not know how to avoid it.
If your opponent is on the 1P side (left side of the screen), then 1A is basically guaranteed after the A+B knockdown. If they tech, then they will be regrounded.
Now here is the first tricky part: if your opponent is on the 2P side (right side of the screen), and if they tech to their left, the 1A gets blocked. In other words, your opponent has to hold 1_2_3G. If they do anything else, the 1A is guaranteed. If they tech wrong, the 1A will re-ground. Also, it should be noted that the semi-avoidable 1A cannot be delay 2G'ed. They MUST commit to the tech early. Another difference when they are on the 2P side is that if you somehow knock them down face up (again, such as if they were in a back turned state when you nailed them with A+B), then if they tech left using 1_2_3G, instead of blocking 1A, the 1A just whiffs completely.
Here is the second tricky part about them being on the 2P side: Even if they block or avoid the 1A, the 1A is somehow "safer" than usual. Normally 1A on its own is -17 on block, but for whatever reason, when used as a tech trap after an A+B knockdown, the 1A becomes -15. Unfortunately, that means you can still be crouch thrown; but it does make the move slightly less punishable for most of the cast.
Also, one additional note. If they make the mistake of teching and being re-grounded by 1A, then FC 1B is basically guaranteed similar to if you had performed the regular 1A,FC 1B combo. If they try to tech the FC 1B after their mistake of teching the 1A, then FC 1B will hit and put them in a BT state as they get up. If they take a regular grounded hit of 1A though, then they can block the FC 1B or whatever else you throw at them while they are on the ground. I wouldn't use 236B after they get re-grounded by 1A because it has some random whiffing issues for some reason. FC 1B seems to be more consistent if you are keeping up the offensive pressure.
Here are so fun relative numbers to chew on though if you are concerned about damage comparison on NH:
A+B,3B = 30+18
A+B,236B = 30+24
A+B,1K = 30+13
A+B,1B = 30+12
A+B,2K = 30+10
A+B,1A (ground) = 30+21
A+B,1A (tech) = 30+29
A+B,1A (tech), FC 1B (ground) = 30+29+13
A+B,1A (tech), FC 1B (tech) = 30+29+18
A+B,4BB:A (tech) = 30+37
Anyways, the move is pretty interesting and has some merits, but not something I would personally abuse since it is launch punishable if you do not space it correctly.
