Do the search but there are basically 2 different types of BCs used today, the back inflate and the jacket style. The BP/wing is a type of back inflate but certainly not the only type. Other examples of the back inflates are the Zeagle BCs as well as several other manufactures. The main difference between the 2 types is the back inflate has some form of harness and tank support that does not contain any lift capability (no air bladder), the entire air bladder is attached to the rear section of the harness. The jacket type includes the air bladder in the "jacket" itself including the pannels that come to the frount. When a back inflate is inflated and deflated the harness never changes so the fit and feel of the BC never changes, in contrast the jacket style tends to sqeeze the diver as it is inflated and becomes loose as it's deflated. Buoyancy and trim chareristics are a good deal different. The difference between most back inflates and the BP/wing is in the harness and tank support. The BP/wing uses a single run of webbing and a metal or less commonly a plastic plate the attach the tank and bladder (wing) to. The other back inflate types use various methods to attach the tank and bladder to the harness. Some use soft backpacks and other use intergrated plastic. The BP/wing is basic in design with no intergrated weights or quick releases. I would suggest you rent/borrow several designs before makeing up your mind. It's a personal choice, I dive a back inflate but I really don't like the standard BP/wing. I prefer designs with intergrated weights and quick releases. That said, if you intend to go to doubles then a standard BP/wing would be the best choice. I find very little difference in the performance in a properly weighted and trimmed back inflate as opposed to a BP/wing.
I am unaware of any jacket style that will handle doubles but most heaver duty back inflates will.