Mynah messes are easy to clean up if you don't let them dry and harden. They do mess more frequently than parrots. We let our mynahs have some freedom for a half hour or more but not necessarily every day. They are content in their large cage. If your have a good size cage, you won't need to let your mynah out, however, it is better to do so.
Mynahs are happy to be out and about and explore around the room.
They really enjoy time out of the cage.