@jakk Others may be more versed here than I, but my understanding is the optimal way to use the Node 2i would be to have both your phone and the Node connected to your wifi network, as opposed to using your phone to instruct the Node via Airplay. As long as you’re not streaming direct from your phone to the Hegel via Airplay, the difference may be subtle (maybe depending on streaming service, too).
Re: Ethernet vs. wifi, i don’t know that there’s a consensus, but general thinking seems to be that connecting the Node directly to your modem/router via Ethernet will give better quality than connecting the Node via wifi. This is especially true if your wifi is not strong, but differences may otherwise again be subtle. More info. here: