Now as for realism, (1) should the Rebels be allowed to attack an enemy head-on? (2) Should the Confederacy be allowed to sneak around? (3) Should the Republic try a slow ponderous attack strategy with very slow vehicles? (4) Should the Empire try to attack with only lightning fast vehicles?
1. Sure. There is no reason why the Rebels shouldnt be allowed to, even if it would probably fail.
2. No. The very nature of Confederacy (droid) armies is that they are loud and attack in large numbers - hardly the right conditions for sneaking around.
3. If you want to go slow, there is nothing to stop them, much like the ability of any side to attack slowly.
4. If you mean Speeder Bikes, sure. They would be easily defeated, but they can try. As for anything else, the very nature of the Empire is the use of large, slow, very heavily armoured ground vehicles, so apart from the Bikes they wouldnt have any fast vehicles.