Ok I have watched this here are my notes
For the next one of these you might want to mute the game, that's honestly way more of a problem than the mic you're using. Hard to hear either of you over characters yelling OHHHHHH HORN CRUSH! or whatever. The music is loud too. There's also two songs playing simultaneously? That's weird.
I am pretty sure Beat Extend + L Bomb is only safe if you block Beat Extend on the ground. If Fortune blocks Beat Extend in the air I bet she could do something like a falling j.MK which keeps her in the air for a while while you let the bomb pass underneath you.
I have seen Fortunes do the jumping back j.LK burst bait then land and do c.LK. It doesn't look like you're in range for that option, maybe you need a different burst bait, idk. In general I don't think burst baits are really worth going for unless you can still get pressure if they don't burst. One of the ones I really like that I stole from 159man is Big Band jump back punch xx cymbal clash. Even if they don't burst there you still get the knockdown so you can do something else after. Dhoppler's suggestion of Fortune j.HK is good too.
Always keep one eye on your undizzy when you're doing a combo. If you're in the middle of an air string and you can see you won't have the undizzy for a ground string, just land and go right into super. You can set undizzy in training mode, try setting it to 10% or 20% or something and do your normal combos, figure out where the best place to cut them short is if you need to do that.
Off raw Drop Kick as Big Band you don't normally get to do an OTG c.MP like you would in the bnb. It depends on how low to the ground you do the drop kick, which is sort of hard to notice on the fly, so I would just go for an OTG c.LP or something cause it's consistent.
Any time you rush punch, buffer a quarter circle and be ready to cancel into SSJ if the punch whiffs. This is important in every matchup but it's extremely important against Peacock because it means she can't teleport to make your Brass whiff.
Crossunder Beat Extend is a really risky incoming. c.MK does the same thing but is safer on block. Beat Extend can still be worth going for to beat their invincible air super, but like, you did it to Peacock. She doesn't have that.
You got hit by H Giant Step a lot this set. If Big Band is full screen he doesn't have anything that'll hit you if you upback, so don't be scared to jump.
You mention snapping in Peacock, I could see it as being a good idea but it depends on the situation. Without two bars Dhoppler doesn't have a reliable way to get Peacock in safely. If he has two bars you might consider snapping Peacock just to not have to deal with the possibility of SSJ > Lenny, otherwise I don't think it's worth it.
In the Big Band vs Peacock matchup you should really Brass way more often. Don't kara punch just chicken jump forward, land, then do it. Peacock doesn't have a lot of great options against Brass, she can't punish an H Brass done from far away with anything but Argus. She also can't beat it preemptively with anything but Argus which is a read that costs meter and doesn't lead to a big reward (you got hit with Argus in that scenario a bunch of times, but, well, don't get read.)
If you're at max undizzy and you can kill but you want to keep the corner, do this:
c.LK c.MK s.HK xx M Brass,
OTG c.LP c.LK c.MPx2 s.HK xx H Beat Extend,
Timpani Drive,
j.MK (triggers undizzy)
Oh yes. You can link an air super after Beat Extend. Just jump up and do it, you have a lot of frames. Give it a shot in training mode. I think it's real important to kill characters with Timpani Drive instead of SSJ when you have the chance because your incoming setups after a Timpani are a lot better.
Some stuff for
@Dhoppler
-Don't call neutral assists with your back to the corner that's like a big ol "please kill Peacock" sign. Not that Peacock ever actually died for this but it's just a bad idea in general.
That's all I got I guess. You won like every game so I don't have as much to say.