I don’t think you’ll find a mated pair of CBB, never seen such a thing. Are they egg layers or pelagic spawners??
I wasn’t aware coral beauties were aggressive. I personally don’t see a problem keeping them together. You may have already discovered that fish do have their own temperaments and individuals may not all behave the same. I have found it convenient to have my frag tank available as well as a QT to keep a problem fish in if it isn’t playing well with others. The scopas tang in my frag tank is there because he just wouldn’t get along with other fish, but he’s a perfect fish where he’s at so I leave him be.
But absolutely find one (CBB) that is regularly eating frozen foods, and in my opinion, if you want a CBB to not pick at your clams, don’t offer it clams on the half shell to snack on lol. Mine will devour mysis, spirulina brine, ocean plankton and blood worms at any time of day.
As far as eating aiptasia I was looking at the tank last night and all of them that were obvious and accessible are for sure gone. My frag tank is a standard 4’x2’x8” lowboy. A buddy of mine that recently put a CBB in his 325 sps dominated mixed reef said that all of his aiptasia have disappeared in the last 45 days, so they do keep them in check (his CBB came from another hobbyist as well so was already trained on frozen).
Keep us posted on whatever you decide to do