For instance could you use one brand for interior, and two different cameras on the exterior (depending on the site requirements, such as a telephoto lens and a doorbell camera in addition to the standard lenses) and have them all controlled and feeding to the same source? Or if you wanted to add a spy camera to the existing system in case someone destroyed the obvious camera what would you need to know to add it?
If you planned on having them feed to a remote app on your camera would that make a difference or complicate matters?