I really don't know if two BR's would start out better than one. I'm not sure of their schooling tendencies. All the pics in the wild show only one at a time, however. And I do know my BR is VERY sensitive of anything that looks like another eel, like the eel-looking grabber tool. He goes right for it when I put it in the tank. But I don't know if he wants to attack it, or be friends with it. And I've held off getting a second BR.
As for which tank, I would think the tank that would have the most fish swimming by his pipe would be the best. My BR takes a constant interest in the coral cats, because they are long and narrow like him, and they always swim in schools right by his pipe (and they often swim into the pipe looking for food). Also the coral cats are great at devouring a silversides that gets loose from the BR.