To show both cameras you need to change the second camera Url when add camera or the image will be duplicated."
What does that even mean? if the first camera is stream and the second stream_1 isn't that a different URL?
I show what is plugged into the USB port no matter what I do, adding a camera as webcam/?action=stream or as /webcam/?action=stream_1 makes no difference, the only camera shown is the one plugged into the USB port. With all your software uninstalled when I plug my webcamera into the USB port the Default camera becomes the camera on the USB port.
"## Considerations