How does access work?
Your host app defines access restrictions during the guest token generation (used by the Superset SDK to display the dashboard). When creating the token, it's possible to define:
RLS rules that can be applied to all datasets used by the dashboard(s) or specific dataset(s). Which dashboards the user has access to. In addition to this, data requests will be checked to make sure the queried dataset is actually used by the embedded dashboard being viewed.
The rules above are the only access restrictions that apply to the Embedded experience. Embedded dashboards are rendered in an iframe without cookie access, so any existing 5X BI session will not be active when viewing it. The embedded guest token is the only authorization method that will be used.