The ANNKE C800 4K cameras support ONVIF so when adding the camera to NCS use the tab for ONVIF Source. Make sure that ONVIF is enabled in the camera.
If the camera do not show up in the Browser list do this:
Add the camera with the tab for Custom URL.
Set stream type to rtsp_tcp.
Set address to:
rtsp://username:password@IPAddress:554/H264/ch1/main/av_stream
and for the low res feed:
rtsp://username:password@IPAddress:554/H264/ch1/sub/av_stream
-Henrik
Did this with my Annke ACZ800 and it works 
Now my question is - What is the camera supposed to return when I find them in the ONVIF Browse window after choosing one? A profile, but where is that supposed to come from? The camera or Netcam Studio X?
When the camera connects with ONVIF the camera will return a number of Profiles that you can select from. Usually it is resolution and mjpeg and rtsp. These profiles are preset in the camera. However, if no one of the profiles is what you are looking for you can login to the camera UI and change these and some more setting. Go to the tab for Custom URL and you will have the exact URL that is used for communication with the camera.