the scientific name makes it more obvious: Plectranthias inermis, it's a Serranidae with the other anthias along with groupers, soap fish and the Liopropoma basslets. where as the hawkfish are in family Cirrhitidae. The Gramma basslets like the Royal Gramma and Black Cap are in Grammatidae family. So it is related to some but not other basslets. The nightmare world of reef fish taxonomy.
My friend had both in his tank for several years, a 29gal, so I wouldn't expect anything more than the usual Gramma tutorial scuffles.
I have heard that they can get very aggressive as the age, I'm not sure why so many places list them as peaceful. I've seen them get pretty big. I've never heard of them bothering corals. A Starry Blenny might be a good choice. Or if you get a small barnacle you could get some Barnacle Blennies, those are really fun.
I would say they are pretty reef safe for a blenny, but I have a starry which is from the same genus who I watched eat a gorgonian like a kabob. I personally don’t like lawnmowers after one that was in the store I worked in started going after stingrays.
