FPS settings in NCS

If my camera does 15FPS max. Should I set my custom url to that as well. Also why don’t all resolutions appear in NCS custom url. My camera can do 1 more resolution than is available in custom url. What does setting to native do?

If the camera delver 15 fps and you want 15 fps set fps to 0 which means unlimted, no change in NCS.
Setting resolution to native do not change the resolution from the camera. So the settings in the camera is what is passed to NCS.

Also if I set up substream in my custom url, will this just allow the live view to display as sub stream and recordings will still be at main stream?

I also mean live view in NCS client

If you set the custom url to be the substream that’s what everything in NCS will be. If you want the main stream add that url as another camera. I suggest you test how it works.