Hello,
we had good results under linux with Microsoft LifeCam Studio 1080p HD and also with the cheap Hauppauge USB-Live-2 to capture PAL/NTSC signal or the deckling blackmagic devices for HD capture, devices which are not v4l2 but can be piped with v4l2loopback on a v4l2 virtuel device (with bmdcapture tool and ffmpeg)
a long time ago, I noticed that the quality parameter of pix_video on macos was important to get the best quality
++b