By “datastructure,” do you mean how your folder hierarchies should be laid out (and maybe where they’re stored)?
For the directories you don’t want PhotoStructure to import at all, mark them as .NoMedia
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You’ve actually got a lot of flexibility with how you set things up.
Where do your files go?
My only main recommendation would be to set things up to make backups as easy for you to do as possible. If that means storing everything on your NAS, because you have that backed up already, then go that way.
(Also: please don’t make the same mistake I made a long time ago and think that a RAID “counts” as a backup. RAID isn’t a backup.)
If you’ve got a larger library, know that PhotoStructure supports “hybrid” libraries.
I’d recommend just using your NAS HDD as your PhotoStructure library, and only switch to hybrid if you need more speed in the future.
What hierarchy should I use?
Every photo and video you’ve taken has a “captured-at” time. There isn’t really any other attribute that’s ubiquitous.
Because of this, PhotoStructure’s automatic organization copies your photos and videos into timestamped subdirectories (if you opt-in).
All other attributes can be then added to your assets via hierarchical tags. Some of these tags are automatically extracted by PhotoStructure, and (many!) more “curators” will be added to PhotoStructure in the future.