Ripping CD to USB drive should be very similar to NAS drive.
In my case, I use dbpoweramp to rip CD to my PC. The file directory folder structure is typical \artist name\album name\track name. I ripped CD in FLAC lossless. I then coped these music folders in both USB and NAS.
In my set up, I inserted both the USB stick and Ethernet cable to the Lumin. The Lumin app on my iPad shows the album artworks from both sources. I can play the same tracks from both NAS and USB stick to do an A/B comparison. I also ripped WAV and AIFF in separate folders, and they all show up in my Lumin perfectly fine.
In my case, I use dbpoweramp to rip CD to my PC. The file directory folder structure is typical \artist name\album name\track name. I ripped CD in FLAC lossless. I then coped these music folders in both USB and NAS.
In my set up, I inserted both the USB stick and Ethernet cable to the Lumin. The Lumin app on my iPad shows the album artworks from both sources. I can play the same tracks from both NAS and USB stick to do an A/B comparison. I also ripped WAV and AIFF in separate folders, and they all show up in my Lumin perfectly fine.