How are most audiophiles going from streamers to DACS

I connect a Cambridge CXNv2 streamer to a Benchmark DAC 3b via RCA digital coax.  I've tried about ten different digital cables and they all sound quite different from each other.  Buying one "quality" cable and being satisfied only works in a system that can't resolve the differences.    Experimentation with different brands will reveal the best for you.

I have the same setup and switched to a RCA coax, with a 1m Silver Solids cable. Cable is custom made and an inexpensive. Amazing sound and detail with that cable.

you can adjust your sound preference with your preamp/speakers and speaker cables

I find Ethernet is very good , and having a excellent dac
like The Bricasti -M3 dac with Streamer module option 
works great ,and even has a excellent Analog preamp section from their M21
if you want to run direct to amplifier ,it’s better then most any preamplifier under $5k.

Wow, a tremendous amount of pontificating, bad advice, and stuff that doesn't apply, If you are going to give "advice" you could at least see what the equipment is capable of. 

First of all, the DAC has USB, optical, and coax digital input while the streamer has optical and coax digital output. So all of you advocating Ethernet, USB, XLR, and/or I2S into the DAC are simply wasting his time since those aren't possible. 

Also a lot of people spouting marketing hype like the Lampizator being the best USB solution possible. Of course that is what lampizator says,. I'm pretty sure the poster has no way to test any of their marketing hype but it certainly looks good on paper. All of the other DAC manufacturers with USB inputs have similar claims of superiority.

And then you get things like advice to use coax to XLR, which isn't even an option without an XLR input, but there is no way to properly implement it if there was

and 

Actually the optical/toslink issue, unlike many sonic preference sin audio, is not a matter of opinion. It does not support high res

all inputs on the DAC support 24/192. I don't know if the Node outputs 192 but that is not a Toslink limitation.

so back to the original question

USB a to b, , Coax, or Optical ? what's the better one ?   I have a Node 2I and a Denafrips ares 2 dac thats  in transit ,

The Node doesn't have USB out (future firmware upgrade with no stated date of availability) so you have the choice of coax or toslink. The cables are inexpensive so I would try it both ways, but my educated guess is the OP will not be able to tell the difference. I certainly would not invest in expensive cables. This is a classic case of audiophile nervosa. The equipment is nice but no amount of cabling is going to make much if any difference.... make a choice... move on.

Hmmm…. So many variations of advice. 
My streamer is a MacBook Pro that supports usb and optical. 
I tried many usb cables and while they all had a differing sound / noise signature all had a glare that induced listener fatigue. I tried the ifi device that allowed one to connect an external power supply to the usb connection. Improvement but still not great. And moving from switched power supply to linear also provided improvement. 
I moved to optical and the glare was removed. I could relax more and listen. And then moving to glass optical cable was a significant improvement over plastic/cheap optical cable. 
Optical support is going away unfortunately.