I had one that was 6 feet high and 4 feet wide after about 12 years, in rich, well-watered soil and full sun. It was beautiful in the Fall. I had to take it out to make room for other plants.

Can it be pruned to give it a more open, tree-like shape?

Yeah, but it doesn't have the right character for that. I have a customer who has an old, open one that hangs over the driveway. It is sprouting at the base and practically shouting to have the old, bulging top cut away and replaced by the basal growths, which look much better. They are keeping the old top instead. Completely out of scale and intrusive.

As mentioned, you can cut an overlarge one off near the ground and get a new, big top only few to several years later--unless the plant is in poor condition. Or try one of the newer, supposedly dwarfer selections. I've seen 'Fireball' at one or two local places already, so these types are making it through the pipeline out to us.

It's got the perfect form for a miniature tree like shape if you plan your pruning cuts.

I was given an 8' tall one - a transplant - by a customer, and I pruned it to a form very similar to how an upright Japanese maple would look.

A few more stems, but basically the same form.

It looked great with ferns and Japanese holly around it's base.

6-8 feet tall and wide. You can keep it cut back, just like you see in the industrial gardens. It does need regular water (not soggy and it can dry out somewhat) but too much drought causes burning bush to defoliate early. The parking lot strips have sprinkler systems. You might want to plant it somewhere out of the spotlight, because 11 1/2 months out of the year, burning bush is U-G-L-Y.