My findings with ethernet cables were that silver plated copper wire works best. Reasonable cost cables (5x over basic ethernet cables) that are silver plated can be had. I have used both Pangea SE (advertises Cardas wire) and AQ Cinnamon ethernet cables. Both are a clear step up in sound to basic ethernet cables. Some of the more expensive ethernet cables feature a thicker silver plating. The question might be how much plating is enough? I stopped when I got satisfactory results with the AQ Cinnnamon.
Value of a premium Ethernet cable
In my current setup, digital music from a Roon ROCK NUC server travels through an Uptone Audio EtherRegen and a short link of fiber, thence to a long stretch of ordinary contractor-grade Cat 5a cable, and finally to a dCS Bartók streaming DAC.
At substantial effort and expense, I could rearrange things so the final length of Ethernet would be replaced by a single run of something like an Audioquest Vodka Ethernet cable. I'm wondering if anyone has experience of whether this is worth the trouble and expense. Well mostly the expense; the "trouble" is the hobby part of it.