There is no limit on the number of KPI’s displayed - on the number of objects/frames that you use in your layout. In fact, you can embed entire layout into a layout and run a sequence.
There is also no limit on the number of dashboard layouts that you create. You are free to create multiple layouts for every site, department, and user group.
Last but not least, there is no limit on the number of users viewing your layouts. You can display your layouts on as many screens, monitors, devices as you need, so go ahead and provide access to your layouts to as many users as needed.