I've never had a lemonpeel, but I've had two Herald's angels. The 1st one I gave a away when I had to get out of the hobby and the second I gave away after a 2 week power outage wiped out practically everyone else (Hurricane Ike). He turned out to be one of the hardiest fish I had. The trick is to find a reliable source for them.
In my experience they were the most peaceful, non aggressive angels and I know this sounds crazy, but it was like they were the peacemakers of the tank. There were numerous times I thought I observed the Herald's angel break up skirmishes among other tank mates. They are by far my favorite angel of all.
As for corals - you can't expect any of the yellow angels to be totally reef safe. Yellows are going to be attracted to fleshy corals like open brains. However I never saw either nip at a coral. I wouldn't say they never sampled a bit of coral slime, but no problems with a coral or clam staying closed or being damaged. I had clams, sinularia, frogspawn, leathers, mushrooms, gorgonian, cups - I did NOT have brains, bubbles, fox etc
I just noticed you're going to put the fish in 30g? Herald's are fairly big dwarf angels and can get like 4+ inches long and the lemon peels get like 5 inches long. Scott Michael recommends no less than a 55g for lemonpeels. And in my opinion that's true for the Herald's also. Although for some reason he says 30 for the Herald's. That may be because Herald's are more peaceful. But just because lemon peels can be little jerks doesn't mean to me that they get a bigger tank!
I personally don't like any angels for a 30, but if you were to do it, an argi might be more comfortable in the tank and they may be a better bet for being reef safe. Certainly you ahve fish that wouldn't be bullied.
If you have brain type fleshy coral , I would not get a yellow angel.
