What level of heat is best when caramelizing?
In my personal experience, "caramelizing" and "quickly" are not things that get along well. I happen to have done a small batch of caramelized onions last night. It took two hours, which is faster than some larger batches I have done, but not anything I'd call "quick" - quick leads to burnt onions, not caramelized ones, in my experience. So - low heat, and forget "quickly."