Any nem may walk around. You will always risk your corals with any choice you make. They can move from their happy place even years after they seem to be settled. I think BTAs have a much less potent sting than a carpet, if that helps? Best advice is try to place it well with appropriate flow, light, and food, pray that it stays; and if not try to watch it to make sure you keep it from connecting with your other corals until it decides where it wants to be. Good luck! Both choices are beautiful!