how much visualization is important for energy work?
It’s not important at all. Feeling the movement of energy is far more important.
Read the work of Robert Bruce.
It can help at beginner stage is but the backbone of energy works are like DarkestKnight said, is feeling.
Visualization is helpful for beginners as it helps you to direct your energy, after a while it does not become needed. Energy work is practically direct magick, without the rituals, the tools, the calling on demons and such for help.