Ethernet and USB cables

Regarding Ethernet (presumably to a server or streamer), there are several choices to make,https://www.thecableco.com/cables/usb-cable/galileo-sx-usb.html

• should you use a CAT cable or fiber optic cable
• which CAT cable to use (i.e., 5e, 6, 7, or 8), 
• will a CAT cable that is advertised as being intended for audio systems provide improved performance in some way over a generic CAT cable with the same designation, and then
• if you believe the above, which "audiophile" CAT cable will you purchase

I suggest first reading about the specific differences between CAT cables from sources like this one, or this one.  For transmitting data in a residential setting, virtually any commonly used CAT cable should do the job relative to bandwidth, data rate, and speed, so the differences in their abilities to reject EMI/RFI and crosstalk may be more pertinent features to look at.  You may also want to look at opinions discussing why audio-specific cables may offer improvements over more generic cables, like here or here.

Regarding USB cables, Belkin Gold is one of the best-regarded of the inexpensive OTS options, and many don't see the need to pay for more.  OTOH, many audiophiles report hearing differences between USB cables.  Supra makes a relatively inexpensive USB cable intended for audio that has been favorably reviewed, and prices go up from there with audiophile USB cables ranging in price from several hundred to several thousand dollars.  You may want to search articles discussing USB cable comparisons (like this one) to help you decide where you want to land on the spectrum.

Everybody hears this stuff differently in their own systems and with their own ears.  I settled on a relatively good quality OTS CAT 8 Ethernet cable for my 45-foot run but then switched to fiber, resulting in only a small (negligible?) perceived improvement in sound.  I do seem to perceive differences in USB cables but happily settled on TWL's $330 “Split Power & Data” USB Cable, after trying several.  However, to my ears, none of them changed the basic sonic signature of my system.