Unlike most WikiProjects, the scope for regional notice boards is very broad, covering a wide variety of regional topics. Additionally, these boards are structured differently than WikiProjects. Rather than attempting to standardize and unify a set of articles, regional notice boards seek to simply improve a broad category of articles.
Regional notice boards are complementary to WikiProjects. It is altogether possible that a board's topics will overlap with one or more WikiProjects, and this is fine. The boards are a more general, informal, and user-friendly means of collaboration.