I would suggest not fixating on what aspect is more important. All these things you mention are good. The idea here, is that you have choices, that apply differently to different people, different times, and different situations. Once more, speaking of the big picture herE. No one is going to tell you that breathing is not important regarding qigong. No one is going to tell you that the visualization isn't important regarding qigong. If you can't do the breathing for some reason, do the visualization. If you can do both, great. This is a compassionate system that allows healing and growth for anyone who wants to pursue it. It offers alternatives for anyone with limitations, to move forward and make progress.
