Thanks so much for your helps.
The NAS can get more and more expensive, when targeting higher specs.
I’m waiting for the specs of the next 2 bay Plus series (DS223+ or DS224+).
I’ve changed my OP to emphasise that I just need a minimal server just for dev:
I don’t need a smooth running server with all data.
It’s great that this static test sample data dump in a standalone mode development server does exist!