Q.bonzai bougainvillea
I read somewhere online about removing leaves from branches to start a formation of the bonzai. I realize it is a personal preference as to the shape one is trying to achieve. I have a thirty year old that I have been pruning or trimming to my desired shape. There is a 24″ circle the bottom is 30″ from the ground . The circle is made from several branches from which I have removed some of the leaves and there are a few flowers, leaves and I have removed some of the leaves from some of the branches.
I'm not clear on your question, but this link may be of help to you with your Bonsai.