As I understand it, a Roon Nuc is a stripped down single purpose PC based Roon Core device... I think its better than your iMac as far as noise (read EMI/RFI) is concerned... However it is still not as quiet as a ROON ENDPOINT might be...
The trick is to run Roon Core on your iMac (Nuc or other general purpose computer) and have an Roon Ready network streamer/player (aka Roon Endpoint) connected directly to your DAC... In my case something like this:
Apple MacBook (Roon Core) -> ethernet/Wifi/LAN/WAN -> Lumin U1 mini (RAAT/Endpoint) -> USB -> Chord Quest -> PreAmp -> Amp -> Speakers...
The trick is to run Roon Core on your iMac (Nuc or other general purpose computer) and have an Roon Ready network streamer/player (aka Roon Endpoint) connected directly to your DAC... In my case something like this:
Apple MacBook (Roon Core) -> ethernet/Wifi/LAN/WAN -> Lumin U1 mini (RAAT/Endpoint) -> USB -> Chord Quest -> PreAmp -> Amp -> Speakers...