LOL, I missed which forum this was in, you'll be fine with an angel then if you won't have corals. You'll also save a fortune on lighting too since FOWLR doesnt have any lighting requirements like corals do.
With a mandarin it's not really about the hiding spots but the diet issues. The one I bought was an ORA one that was supposed to be eating pellets. Well, got her home and no go on pellets or ANYTHING I fed her. She just hunted for the pods I had in my tank. It took about a month of multiple feedings a day and an insane amount of time and effort but she started eating frozen food for me. I also had to shut off all water flow and target feed her with a turkey baster full of food. If I had to do it again I probably wouldn't. Even almost a year later I have to target feed her and watch her constantly to make sure she is eating.