Do different streamers really sound different when using an external DAC

Yes. With their DAC. But I read that if you use the SPDIF digital coax out, only 24/96. Bluesound's website does not clarify.

If I am wrong then I'd sure like to know!

I can weigh directly in on your situation. I have a Node 2 and bought a Mytek Manhattan II DAC with network card (streamer). Initially I set it up as you have with the Node 2 going into the Manhattan via high quality Coax. Then I directly compared it to the network card in the DAC. No question that the Mytek network card sounds better than the node 2 streamer. 
I will say that the difference between the DAC in the node 2 and the DAC in the Mytek was much greater than the difference between the streamers. But yes, the streamer made a clear and noticeable difference. The only reason I ever use the Node anymore is if there is something on the radio I want to listen to - my brother-in-law is a DJ in Irvine CA and I like hearing his show - and the Mytek interface doesn’t allow for radio streaming. 
Matt

I responded before realizing I was the first one to actually directly address your initial post. The Mytek is fully MQA compatible - as is the Node 2 (note: I have the 2 not the 2i).  I stream both Tidal as well as Quboz. I’ve not heard a particular difference between those 2 services which surprised me as most on here tend to prefer Quboz. Let me know if you have any specific questions - I’d be happy to share. 
Matt

The BS Note2i does not sound good at all without the External DAC. I have to turn on the volume high but it is a convenience. I have been exchanging the Bifrost for the Gungnir and will see in the next few weeks. Hopefully, the Gungnir is much better than.

True that the node 2i output is only 24/96 if using an external DAC. That being said, resolution isn't everything. Implementation is very important.

A bit like cameras where you chase the megapixels as the only determinate of image quality when there is so much more like lens quality that goes into the equation.

I use wifi and have zero dropouts. I have never considered a hardwired ethernet connection.

I have compared the quality of the same file via a drive hooked into a computer on my network vs the same file on a flash drive connected to the USB input of the node 2i and found little  discernable difference. You can't get any more direct than the USB input so I doubt in my set up a direct wired ethernet would make much of a difference.

I have thought about a better power cord for the 2i so thanks for the input on that, lowrider57