Total War are already familiar with using a strategic map.
Mission selection is a matter of choosing an enemy controlled territory that borders your own. As you take over territories, you'll eventually come upon a stronghold of one of the rival houses that leads back to that house's home planet. The final victory comes when you warp over to your rivals' home planets and give them a beatdown in their own living room. The choice is yours. Boom Elevation does play a role in firing range and sight range Mission planning Mission selection isn't just arbitrary though.