You are not forced to use an XA transaction just because you access a remote queue.
You have to use an XA transaction, if your MDB does another operation on multiple transactional resources, and you want to commit all units of work or nothing (this applies both to local and remote resources).
As for your 1st question: You should use CMT, because it's easier, and BMT always acts as a transaction barrier: The global transaction is never propagated into a EJB using BMT.
As for your 2nd question: I am not aware of an option to do this. I suggest converting it into a CMT MDB.
Related: Why do EJB beans with bean-managed transactions act as a “transacation barrier”