HI Reece Heald,
The data access is purely what we handle at the Entity level and Page level using Xpath.
For your useCase you will have to keep in one thing while developing.
Whether the report page is a Normal page with just a list of data or a Visualized page with a chart, you can keep DS flow to load the data. In the microflow check the current user and check if he is a Manager or employee. then retrieve data based on the user Role and other constraints you have.
You can always set Xpath Constraints in your Domain Model for the user role.
Hope it helps .