I have 6" adult emperor in my rsm650s (approx 150 display tank size) and he doesnt touch any sps or softies HOWEVER he did nip at my scolys and my trachys. I took those out and he hasnt bothered anything else including my lobos, duncan, toadstools, elegance coral or any inverts including my skunk and peppermint cleaners.
That was worth the trade imo.
I do always keep romaine lettuce on a veggie clip all day, and dried seaweed (purple and green) everyday so he has plenty to nibble on at all times (which he does)
He eats frozen and live blackworms like a pig.
Though large angels are all individuals I think keeping them well fed with veggies to always munch on increases your chances of him not going after corals.