Is there a difference in an I²S cable RJ45 vs a great Ethernet cable?

No, I got a Tubulus Argentus instead I found used. I have nothing to compare it to one and done.

@fthompson251 ...

... did you end up trying the DH Labs HDMI  cable between your Denefrips Hermes and your Venus II DAC? Did you hear a difference over the connection you were previously using? I have Hermes DDC connected via I2S, using a 1 m DH labs HDMI 2.1. It is my first try using I2S, and I am interested in if your were satisfied with the DH Labs, or if you moved on and if you did ,why?

@fthompson251 If your question is about the length of my DH Labs cable, it's 1m. Anyways, I²S connections, even the balanced ones should be kept at minimum.

@Habermas

How long DH labs did you get? I want to try this between my Dinafrips Hermes and Venus II DAC.

So just received my DH Labs HDMI 2.0 Silver plated OCC Copper cable. It cost me less than 100$ with shipping included and is easily an improvement in clarity and focus over my Audioquest Carbon HDMI I used until now that costs double its price. It really enhances the holographic qualities of the Holo May KTE. Easy recommendation in the "budget" category me thinks.

Has anyone done an A/B comparison between HDMI and RJ45?

AVplay HD-300 has been mentioned.

Revelation CryoSilver Reference HDMI

From their website : 

Tubulus Argentus i2s Cable

Very neutral and detailed i2s cable, with a realistic, transparent, open and width stereo image!

Review Quote:”…The music gains in detail and it sounds spotlessly clean. There is lots of space making the stage wide and deep combined with a beautiful powerful and layered middle area. The improvements ensure increased involvement and you are dragged into the music. You get the feeling that nothing is getting in the way of the music, as if there is no cable at all…”

I second this question, using for now an Audioquest Carbon HDMI, but not much information out there on good HDMI cables for I²S.