For 350 pages, you don’t need a database. Check out this post, for example: Server response time
If you simulate the hierarchical organization, it has the advantage, that you don’t need to filter a complete folder and don’t need to implement the fields to filter by. So if there is no reason not to use that structure, go with it, I’d suggest.
Users or pages: If you don’t need a login for those user, no need to create users and you have more freedom to organize the members.