What cable type (TRS or TRRS) is appropriate for connecting my Zoom H5 to my Sony A6400?
Use a TRS cable. Make sure you reduce the line-out level in your Zoom H5, otherwise the audio in your camera will peak all the time.
The quality/purity of the copper in the cable is irrevelant. This OFC vs. OCC is just marketing-blah-blah. Apparently no manufacturer has been able to prove any discernible difference.
A real problem is that these 3.5mm jacks and cables aren't durable in the field. They just break too easily.