A dashboard visualizes source reports. Each component needs a report whose population, grouping, and aggregate answer the intended question. A metric, table, or chart can't correct a bad source. Keep the source reports recognizable so another administrator can inspect their definitions.
The running user affects data visibility. A dynamic dashboard uses the viewer's context within its supported behavior, while a fixed running user supplies a defined perspective. Folder access determines who can find the report or dashboard, but it doesn't grant every underlying record or field. Test as the intended audience and check whether a sensitive aggregate could expose information beyond the request. This local simulator evaluates the selected user's record access rather than connecting to hosted report subscriptions.