Between a Node 2i and DAC: Does Coax cable quality really matter?

Yes, you will hear a difference between cables. Nobody can say for sure if there will be an improvement. If you feel an upgrade is in order then audition other digital coax. Order from dealers who offer a trial period. 

I auditioned quite a few S/PDIF cables, also returned a few. Finally I found a cable that significantly improved my digital setup.

+1, fuzztone.
The only way to know by trying couple of cables in your setup. I say this, DH Labs makes very good digital cables. Here are couple of recommendations,

https://www.tweekgeek.com/audiophile-cables/oyaide-db-510.html
https://audioenvy.com/product/home-car-pro-interconnects/digital-coax-3ft/

I can send you the AE Digital Coax for you to try. If interested, PM me your address. 

Changing to a good coax made a big difference for me. Using AP Crystal digital solo. More clarity, better bass.

Yes better cable helps but the bigger difference for me was adding the iFi SPDIF iPurifier 2. Amazon carries it so risk free trial.
-Alex

@rareace, the iFi does improve the SQ in several ways, music has more weight, wider deeper soundstage, more dynamic. I'm also using a Swagman Labs LPS.

What's the difference between  iPurifier2 and the first generation?