Are we just going to ignore the actual game lore though?
Let me break it down: When Astarion ascends, his dialogue changes. He says something along the lines of "seven thousand souls were sacrificed yada yada my d is so big now". We know that cazador turned every last one of the victims to spawn, therefore they are just like Astarion. Vampire spawn. Their souls were sacrificed in the ritual, something they had to perma-die to do (as shown by the main spawn exploding and the vicera in the cells as ypu exit). This means they had their souls. Boom.
Now lets address why that may be if vamps are supposed to be soulless. Might it be that they are vampire spawn? Not quite the real thing? Maybe. Im unconvinced, because if so then cazador shouldn't have been able to work as a stand in. Nah im betting its something more along the lines of an anchor not unlike a lich sort of. My guess? The contract carved into every single spawn -the same one he carved into cazador to sacrifice him- reconnected them to the souls that once were shed in an unholy deal of immortality. This is all speculation on my part of course.
The only thing that is not speculation is that for some reason, all 7k of those vamplings had souls, and only larian knows why for sure.
