Toslink is limiting for two reasons: (1) The signal undergoes dual conversion - first on the transmitting end from electrical to optical S/PDIF, then on the receiving end from optical back to electrical and (2) It was designed as an inexpensive S/PDIF link for consumer disc players and no high-precision transceiver modules exist.
When Stereophile and other test labs test for jitter, the optical output almost always has much more. Is this just a measurement thing and not really audible? I don't think so. Subjective listening on sources with both coaxial and optical S/PDIF 4 out of 5 times sounds to me like the coaxial source is more in focus and the optical is blurred a little, to use a photographic analogy.
Given a computer or streamer with a PCIe slot with more direct connection to the processor, my preference would be a soundcard with coaxial S/PDIF or AES/EBU outputs. As this is not possible on a laptop or slotless mini computer, you have to go with what works best with what is available (USB or optical).
USB implementation varies widely, with some hardware giving good results stock while some others require external device bandaids.
As far as optical, the previous recommendation for Lifatec Toslink cables is a good one. I'm not sure about huge advantages over short lengths given the state of Toslink transceivers, but it eliminates any doubt of the cable adding problems and you're only paying an industrial parts premium, not an absurd audiophile blue sky premium.
I've seen too many problems (dropouts, etc.) using Toslink to mini-Toslink adapters that I won't bother with them. Get the properly terminated cable to start with and forego adapters.
Steve