I think Miami could be the best option for a Ja trade, not just because of the playing style there and the Heat Culture, but also because I think Morant will be motivated with a team around him in Miami with a solid roster.
Although Memphis will have a problem at the point guard position, Bruce Brown could be a solid starter/6th man and obviously Herro beside Jarren Jackson and Bane would help the Grizzlies playing idea this season with quick ball movement and less time with the ball in their hands (which Morant wasn't happy with).
Finally the Pelicans asume a great role player such as BC.