If you add an external DAC to the Node 2i, you will not be able to listen to MQA. I purchased an external DAC with my Node 2i and preferred the Node 2i played by itself. Bass was better with just the Node 2i and I thought the imaging was also better.I will jump aboard this slugfest as well.
Node 2i onboard DAC is ’average’ at best. At best. Definitely tuned for a soft, inoffensive sound at the expense of dynamics, detail and soundstage.
MQA is a can of worms. My net on it is ’iffy/sometimes’ benefit at best, and it is a pain in ass to navigate the layers of hardware issues... given the weak cost-benefit, one is better off getting a good non MQA DAC. Much of the time, the 1st unfolding gives you the lions share of the total benefit, which non-MQA DACs can typically do with the right streamer.
This being said... digital out of Node 2i is fine. Use it to feed a decent $500-1000 DAC (used or new) -- the improvement will be stunning. Any Chord DAC (including the lowly Mojo) will render the sound of Node 2i DAC dull and lifeless...on Redbook resolution. As will any of the DACs on my list above...