Yes- re coaxial- the problem with the S/PDIF is that it’s a 75 ohm connection and there really isn’t any true 75 ohm coaxial cable that uses RCA terminations. That’s why I use an AES cable, which in fact can be a true 110 ohm termination, and that matches the spec of the AES termination itself. Some will argue that impedance mismatch isn’t that big a deal, but I figure if I can avoid a mismatch, that’s the way to go. BTW, a BNC cable can be a true 75 ohm cable.
So, my thought is- 1- use a quality cable; 2- termination is important; 3- avoid impedance mismatch.