When constructing a group exercise class that is not dance based, is it best to count reps or do exercises for time?

I want to do a calisthenics/cardio class. I want to make sure the class has the flow and intensity of a cardio aerobics class but with muscling building whole body exercises as oppose to classic aerobic moves. I know music is a important part of a group exercise class and keeping to the tempo is important to keep the heart rate up. I