I've tried Strawberry Guava trees with no success at all. What I mean by that was, our Meller's didn't like it in t he least. Maybe he knew something I didn't when I bought but he certainly did not like it. I ended up with a hibiscus in his cage and I use an old established schefflera outside when we free range him on the weekends.
I trim our hibiscus almost monthly. It grows rapidly. The trick to it is pick the major branches you want to keep and visualize the end result. prune around the major branches, leaving some young sprouts to fill in the gaps etc. It's a little intimidating at first but once you get the hang of it, you'll start wanting to keep bonsai!
Fruit trees typically don't do well indoors. They may under the lights of a cage, but young fruit trees aren't as strong and hardy like older larger individuals.
Good luck,
Luis