On Suns a "ls -lL /dev/rmt/*" will give you a better idea of whats happening. You don't have too many special files, it's supposed to work that way. Each file specifies various different behaviors to be applied during open, read, write, and close calls on that device.
Your example is just rewinding the tape. This is one case where it doesn't matter. It doesn't matter what tape density you pick since rewind is rewind. It doesn't matter is there is an automatic rewind when you close the device since you did a rewind anyway. It doesn't matter what woulda happened had you tried to read past EOF since you didn't. So yes, in the example of just rewinding the tape, it doesn't matter. But someday maybe you will do something with your tape drive besides rewinding a tape. Then it will matter.
The various options are documented on Suns on the mtio man page. Read that and see if you still have any questions.