a 12' boa (of any subspecies) is very uncommon. Likely a female BCC.

Male BCIs typically stay in the 6-8' range. If you feed conservatively (not starving it, but not stuffing it either) you can keep them towards the smaller end. Feed once every two to three weeks as an adult.

They're typically very calm and docile animals, though there are exceptions. They're a good step up from a ball python.