Learning as we go: after some googling and contemplating there is one area that needs clearing up.
The OP was enquiring about various RCA analogue cable designs I believe. I'm sure there can be sound differences between them, single channel coax 75 ohm unbalanced or 110 ohm balanced (3 pin) are among them. One connector, one channel.
A coax with RCA connectors is "probably" an s/pdif digital only cable. The single RCA connector has a stereo digital protocol and cannot be used as a single channel analogue cable.
As a side note: My Oppo 203, used as a transport, uses one of these single s/pdif to connect a Bifrost 2 DAC. Unfortunately the s/pdif-optical output is not working correctly (verified using an optical cable) A center vocal track is slewed to the right channel, while using an HDMI cable out of the Oppo dac is perfectly centered. Any advice to correct this would be very appreciated as for 2 ch cd output the off centered output is noticeably more resolved with lower background noise. Bummer!