Have a look
here and
here.
The flat cables do not seem to meet either Cat 5 or 6 spec due to their construction. Empirically, I have been able to reach transfer speeds that would put them in 5e territory.
That said, ethernet ports on any Sonos device are exclusively 10/100, so if you're using these cables for nothing but connecting Sonos devices, no need to shell out for high end cabling.
Interference on a cable should be negligible compared to the wireless interference that Sonos has to deal wit, personally, I've never experienced any issues with a wired Sonos speaker.
Life is what happens to you while you're busy making other plans (John Lennon) --- Living room: Arc, Sub, 2x One - Kitchen: One - Bedroom: Play 3 - Office: Beam - Bathroom: Play 1