The attack grab wasn't a counter hit (Kilik ducked), so I'd guess just the B input on hit in the mixup string. If the alternative to the B isn't a low, it seems like it'll be a bad option. But yeah, based on the duck, I'd hope it is.
Due to A+B's recovery frames seeming to be reduced (based on SC5 animation) and the fact that they even showed A+B there, it seems the 6B is a followup, probably only on successful persona change.
The GB on 4B+K.B is nice, and it looked like they may have landed close enough for a 666B, should that even exist anymore.
Her throw on RE's B input is nice, but I worry it's breakable since she actually grabs them. This could mean one of her Gloomy grabs is this rather than mirroring Jolly's.
Her A now has a K mixup option (outside of Soul Charge based on the energy pulse happening AFTER the kick lands). This could be exclusive to Gloomy since that's the persona shown. The BE followup to the kick seems to be a mid version of her 4A, it's also a GB. If 2A+B exists and stuns, it's potentially a stronger combo than 66K's attack throw.
All CEs in this game shown to date (aside from Astaroth's) are attack throws that work on standing or airborne opponents. Based on screenshots also provided, her CE's visual effects change colors (Jolly is Yellow, Gloomy is Purple). This could mean that the Updraft-style smackdown isn't going to be present in Jolly's version of the CE, assuming they do something similar to SC5's CE.