Typically spawn areas are around the A and C capture points. So, let's say you start by A, if you capture B and keep running A and B to keep them, the enemies will mostly spawn by C, allowing you to control the game by keeping them pinned. The unsymmetrical maps usually have 2 zones that are a little closer together so it is easier to capture those two, and pin the opposing team by the third. "Switching spawns" is when your team has 2 points, let's say A and B, and you have a teammate or two that keep going to C, making it so the enemy starts spawning around one of the zones you control, giving the enemy a better spread on the map, and possibly allowing them to capture the second zone.