Is the RCA camcorder output analog?
The best way to answer this definitively would be if you know the model of the camera.
RCA cables from video cameras are nearly always analogue signals.
It is possible for a camera to have both digital outputs such as HDMI and SDI, and analogue outputs such as component or composite video from RCA sockets.
The analogue outputs are almost always standard definition (ie 480 or 576 lines of video).
HDMI outputs are usually high definition 1080 lines (or possibly 720 on older cameras, higher on newer 4K cameras).
If you are asking how to capture video from a camera with HDMI output in high quality into a computer with USB3, I would use an adaptor such as the Elgato HD60 S Capture Card.