I became a believer in conditioners affecting SQ quite by accident-bout a monster device to deal with tv issues and noticed better sound thereafter.
So I am in the camp that isolation is a good thing.
I have no idea whatsover whether and ethernet cable cd injure sound transmission or not or even if it cd at one place but not another.
I wd suggest that unlike other audio things it doesnt cost much to experiment and again unlike other audio equipment changes a cable that doesnt work for the audio as one hoped can still be used for other networking connections so not much loss overall.