If it produces a colour image on your monitor, then you've got all 3 channels. Luma by itself gives monochrome - it's how they upgraded the old broadcast systems to support colour without cutting off all the existing black and white TVs.
Whether you need the colour component is up to your use case.
If you need to transmit the data, then you need to look at H264 compression. The Pi has hardware H264 encode acceleration, so it can handle it easily.
Both USB sticks and the ADV7282M produce one of the family of YUYV
formats. This isn't handled natively by the video encoder, but I'm about to push changes which should mean that it does an efficient conversion using a different hardware block. I'm testing it with a a different chip that is producing 1080P60, so NTSC is easy in comparison.
The PiCapture does a lossy conversion to a Bayer format in the FPGA, but that does mean you can use the standard raspivid camera app to capture your video.
Which solution is best? Not one I can advise on.
If you can find a USB device that works, then that's the cheapest option. But be aware that it will be stressing the USB system, and the ethernet connection shares that same USB bus.
The other two solutions are currently either not commercially available, or fairly expensive.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.