When "placing" at runtime I assume you instantiate them. They will then be GameObjects, which you can edit through code. If your GameObject has a Camera GameObject as Child you can use transform.Find("GOName") to find the camera gameObject, and then Oject.Destroy() it or just deactivate it.

However, this is bad practice as it requires names to stay the same without breaking the code. You should really only save assets exactly as you need them. If your asset doesnt need a camera, it should not have one attached. You should take that little time to clean up your assets, because it will eliminate a lot of time consuming future problems.