Both DMS and ADF are fine for archiving NDOS disks.
These unitialized disks don't contain any AmigaDOS files, they can only be read by the little piece of code stored in the bootblock of each disk. That's why they are called NDOS (Not DOS). Storing them as ADF or DMS (with NOZERO option) is the only way to archive these disks and running them on an Amiga or emulator is the only way to access their contents.
