You asked some good questions, and you got a lot of good answers.
The only thing I'll add is that your BC may be your best opportunity to spend hundreds of extra dollars without any discernible performance advantage over lower cost options.
What do you really want a BC to do? 1) Assist in buoyancy control by adding and bleeding air, 2) Give you some place to store and hang whatever dive accessories you bring into the water, and 3) Secure your tank (can be accomplished without a bc, but not by many divers nowadays). That's it. You can perform these functions for <$500, or you can perform these functions for $1,000+.
The more you dive,* the less you'll want out of your bc: less bodily restriction, less weight, less stuff hanging off it, less padding, less weight needed to bring you and it down from the surface. That means the more expensive option will probably serve you less well than a well chosen lower cost option.
*recreationally, that is.