My PBT experience went like this....bought a beautiful specimen right from the big display tank at Old Town Aquarium and paid Sa too much for him. Got him home and put him in with my triggers, naso, and lemon peel. No aggression, but in one day, covered in Ich and in a day or so, all fish were covered. Moved everyone from my 90 into my old 55 and treats with cupramine. At about one month, the fish couldn't handle the small conditions and were beating each other up badly. I was forced to put them back in the 90 even though it had only been one month. No ich ever since then and he only shows aggression to then naso, but it isn't consistent. I've had mine since about 2010.
My advice is to definitely QT a PBT because it is HIGHLY likely to be carrying ich. I'd worry about the aggression second.