I've got a few pocket doors, and am installing one more. In my case:
1) All doors are trimmed with stops on both sides and the top like a conventional door. None are peekable.
2) My doors are removable when all the stops are removed. There's a lower guide that has to be removed, but the door can be tilted and lifted off the overhead rail.
If yours aren't removable, to paint the interior of the jamb, I'd wrap the edge of the door in wax paper or plastic sheet, open the door, and paint the jamb. Slide the door back and forth a bit so you prevent a paint bridge from forming. When the paint dries, open the door and remove the covering.
3) The gap at the top is adjustable, individually on both rollers, to allow adjusting the gap and levelling the door (or making it even with the jamb on the closing side).