They can all be different. I personally would grab a young one up to a year old and work with it. I bought a beautiful, male locality boa. A Barranquilla, Colombian and he was pretty easy going out of the box, but then got a little defensive for a few weeks.
I would never be afraid of a small boa, and would suggest you keep working with it.
Nothing against royals, but they are not in the same league as BC's. You will quickly find your BC, should you get one, will eat, climb, explore and become a favorite in your collection.
There are several threads in the Red Tail Boa forum here that I suggest you read. I don't have the time right now to delve into the biology, and feeding regime of them, but you will find a boa constrictor to be a very rewarding and easy keep if you decide to take the plunge.
First suggestion is to buy THE COMPLETE BOA CONSTRICTOR By Vincent Russo. Also take any internet posts by Gus Rentfro as gospel.
This is an old picture of my BC at a few months under the 1 year mark. I probably had him in my possession for about a week here.
http://i772.photobucket.com/albums/y...a/IMG_1012.jpg