The ARCamera prefab is the composite of one or more RenderCameras and a ARCameraBaseBehaviour.
You can choose world center in the inspector. See ARCameraBaseBehaviour.CenterMode for more details.
You can turn RenderReality off to disable camera background display.
RenderCamera is a general camera in Unity. You can change the near and far clipping planes in the inspector.
Camera projectionMatrix including FOV are controlled by EasyAR.
The RealityPlane is a plane where images from camera devices are displayed. The plane texture contains the whole image from camera. Relative transforms between RealityPlane and RenderCamera are controlled by EasyAR.