To address issues with unauthorized access to sensitive data and dashboards, the best practice is to create separate apps, datasets, and dashboards for different user groups and then manage their sharing settings appropriately. This allows you to maintain data security while ensuring that users only access the data and insights that are relevant to their roles. In this scenario, applying separate apps for managers with defined sharing rules will prevent users who shouldn't have access from seeing sensitive data.
Reference: Managing Data Access and Sharing in CRM Analytics