They will naturally assume the posture of a small tree, so barring any obviously ungainly branches, et al, would leaves them to their own devices. Those tall and narrow can be clipped on top to encourage branching.

I have 2 of these I planted almost 2 years ago. I bought them as bushes in 5 gallon buckets. It will grow fast, so you need to prune often in spring to thin out the desire to turn back into a bush. I trim off all new growth at the bottom and around the middle area where the main branches split off. This trimming encourages the growth back up into the canopy and growing taller. I trimmed 2 weeks ago, but have to trim again this week. Maybe 1-2 more trimmings will be necessary. My trees are now 6-8 feet tall and they bloom frequently. A neighbor 5 houses down has one that's easily 15 feet tall and looks like a tree, which is why I got them. It's perfect for a small space between houses in an HOA. The one pictured here actually has 2 trunks out of the ground, but you can have more or less primary trunks. Oh, and this is the only tree that has survived whatever chemicals the house builders dumped into the soil.