Marine Betta (A.K.A. Comet), as blaxsun mentioned, is probably your best bet - most groupers get way too big and aggressive for a 75 gallon. The Bluetip Shortfin Grouper you listed is another good option, though, as are other members of that genus (Paraplesiops) but they’re rarely available in the trade and they’re quite expensive as a result.
From my understanding, a Clown Grouper will eventually get too big for a 75, which normally isn’t really an issue (you can generally figure it out by when the fish starts showing signs of stress and just rehome them), but big aggressive fish like groupers are generally pretty hard to rehome, and, for Clown Groupers specifically, they can also release toxins into your tank when stressed. So, you’d need to rehome it before it outgrows your tank or you’d risk having it potentially nuke your tank.
Just my two cents on this.
If you want grouper-like fish, but they don’t have to be groupers, I’d recommend something like an Indigo Hamlet, Belted Sandfish, or Sand Perch - not the same, I know (I love the look of groupers), but smaller, pretty fish all the same.
