Almost sound like your in IT... we have a common phrase; backup, backup, backup and; Did you backup today? Did you?
All my media is on a second drive then I backup to a second pc then to a external via bat file, bada bing bada boom. People may say its excessive but that first time you lose everything... even if you still have it on CD your looking at weeks, months to rip it all again.
Yes storage always double what you currently need, at least.
I would be curious to know about any lose of sound quality over usb, is your Nuc connected by hdmi? Could you have the same song on the Nuc then play over usb and hdmi and compare?
In the last few days I have revisited playing over DLNA. I currently have my Nuc connected to my pre by hdmi, the Nuc is running Plex. I wanted to compare so tried it from my Oppo using Dlna and preamp using Dlna. Unfortunately there is some improvement, I say unfortunately because over Dlna I lose the nice browsing and playing on the tv experience with Plex.