Two template files are provided with the Maya installation that enable you to easily create overrides to set specific cameras as renderable or non-renderable. The .json template files can be found in the default user templates folder (<Documents>\maya\RSTemplates). Right-click your layer to import either of these templates.
RemoveRenderableCameras.json: Import this template if your cameras are set as renderable in your scene, but you want to set a subset of these cameras as non-renderable in your layer. For example, if camera1, camera2, camera3, camera4 are all set as renderable in your scene, you can create an override to set camera1 and camera2 as non-renderable in Layer1.
After you import this template, add the cameras that you want to set as non-renderable to the Remove_Renderable_Cameras collection.
SetRenderableCameras.json: Import this template if your cameras are set as non-renderable in your scene, but you want to set a subset of these cameras as renderable in your layer. For example, if camera1, camera2, camera3, camera4 are all set as non-renderable in your scene, you can create an override to set camera1 and camera2 to renderable in Layer1.
After you import this template, add the cameras that you want to set as renderable to the Add_Renderable_Cameras collection.