I can't answer all your questions, but I can answer the question about sensored vs. non-sensored. The higher KV motors can be prone to cogging with sensorless, and in general a sensored motor is smoother throughout the powerband, especially down low. There are some escs that work in sensored mode down low, then switch to sensorless up high to increase efficiency.
Why one esc is an "SC" model vs it's regular version I'm not quite sure, although the SC version tends to be able to handle 550 size motors, and perhaps has better heat control for the greater loads put on it. Don't quote me on that, since I'm kind of asking the same question elsewhere (can the GTB handle a 550 motor?) in this forum.