There are numerous ways to setup and the best depends on the individual. You will probably get several different answers to your question.
Some questions for you. What does your internal network consist of. Wireless, Ethernet or a combination?
The Nucleus should be wired to the router. Wireless works depending on the strength of the router but would encounter problems at various times. Endpoints can be wired or wireless but wired is the most reliable, at least for me.
I would have the Nucleus wired to the router with your music library on a SSD drive internal to the Nucleus and use the NAS for backups. From there its hard for me to say because I’m not familiar with the capabilities of the devices you mentioned.
I have my NUC/ROCK in a media closet next to my network and surround system components with HDMI from NUC to Receiver, USB from NUC to OPPO 205 DAC, Ethernet to PC/DAC in the bedroom and Ethernet to a Roon Ready speaker system in the kitchen.
That works best for me, in my home, with whole house music but would not be best for everyone else.
Hi Barry, I just looked up your devices and it looks like the Nucleus should be able to use the Auralic Aries as an endpoint via wifi provided your wifi is robust enough. The Aries is Roon ready. The Arcam Air DAC doesn’t have a USB input, but you should be able to connect to the Aries using Toslink or coax. Then RCA’s to the Marantz and you should be good to go. For the Nucleus, Mike’s advice is correct. Best practice is music on an internal SSD, use the NAS for backups.