I had a few over the past couple weeks that developed like that. When the bees in the hive are young, they seem calm and tame. Since they had an aggressive genetic tendency when they transitioned to foragers and older they got to be no fun. Certainly not super mean en-mass enough to be think africanized but certainly enough of them followed us around the yard and constantly head butting the veils to tip the scale against them. Hives like that are actually great candidates to put out into the remote locations as deterrents for two legged lookyloos and damaging critters such as bears and skunks. However, they are really not ones to tolerate around the backyard or have where there are neighbours that you actually like.
I have requeened all of those testy ones. My suggestion for killing the brood is to significantly shorten the timeline of the correction. If you leave it, it will be 5-6 weeks before the transition to the replacement genetics of tamer bees is mostly done. While having to put up with mean ones all that time during the old brood develops, emergences, ages, dies. By removing the brood up front, removing the genetics, making a hard-stop of her offspring, the timeline to seeing transition is shortened to 1 - 2 weeks as the old bees left are dying off. Yes, there will be a dip in the hive population 2 weeks out. But that actually means less mean bees in the air doesn't it ?! Better that than the alternative of filling the airways with even more mean bees. If there are other hives in the yard, those can be used in 1-2 weeks out to boost along and level the hives by donating a frame of capped brood from time to time.
Good to know that the other hive making cells is a caught swarm, and thinking they are replacing the old queen is definitely on track. The waitNC is a good tactic in that case, so long as they have enough space they are in now. It is best to reduce the number of cells down to the two nicest fattest and one well made spicy one. Three total. If you have any idea what day those cells got capped, you can then project forward on the calendar to when you can expect emergence, mating, and finally laying to happen. That way you can avoid disturbing the hive on those period of days that they need to be left alone so the new queen(s) can get sorted out and become queen rite. If your plan is to let the hive develop cells and mate.. then absolutely you must also do your best to destroy-kill or contain the drones in the mean hive, as in my first post. Else your new queens will likely mate with some mean drones, and you will be back in the same situation with this new hive, or both hives, being mean in 1 1/2 months.
For your considerations, Hope that helps!