To use external USB camera and an android device with VSight Remote, your android device should support USB OTG.
You can check if your device supports USB OTG by checking specifications under communications either on your phone settings or online. It should show either USB On-The-Go or USB OTG.
Once the USB camera is plugged to your phone, VSight Remote app should recognize the external device and ask the user to give access. Once the permission is given, user can switch camera device and select camera resolution. You can always change the resolution in the upper right corner of the session.