young BPs can be nippy and a bit agressive, but thats mainly because they are scared, they typically grow out of it.

i think that when you get one that has a good temperament and that is relaxed, you can actually expect a puppy-dog tame snake ^^ its the norm, not the exception. and its perfectly fine to ask a breeder about temperament.

yes, some people call them things like "slugs" or "valium snakes", and criticize them for behaving more like a decorative object than a snake. (as in: doing pretty much nothing). but if you want a really tame snake, a BP is the right choice. even a tame corn snake or boa constrictor that wont bite you will move around much more when you handle them.

you can handle them a lot, its just that when you first get them, you shout take things slow and give the BP a week or two to relax and get used to the new home. but then, daily handling should be no problem. (except that they need a day or two of rest after they had a meal, and might not like being handled when in shed).

about handling the BPs before purchase, some small breeders do not like to reveal their collection to others, others have less reservations, and then there also are reptile shows, so im sure it can be arranged.