Maybe I should use the word health instead of strength. I just want to build a nice canopy, not to large. Why would people prune their bonsai down if it is not healthy..
You're not in that phase of development yet. To summarize the overall process, you start out by growing, and then, when the tree is vigorous, you cut it back. It starts out with long stretches of growing before pruning (years in many cases), and gradually, you prune more frequently until you get to the point that you are refining the tree, pinching new buds before they are even finished growing. If you try to jump ahead to the refinement phase before the tree is ready, you could kill it. Proper energy balance is that important. Even highly refined trees still need a break from time to time from refinement techniques in order to regain some vigor.
You just bought your tree. Give it a year to ensure it has enough energy before you mess with it too much. It's probably fine if you want to remove a handful of branches that you don't plan on using in the final design, but overall, you should let the tree accumulate more energy.
