@WebPortal as it is mentioned in the licensing details, Power Apps per app plan allows individual users to run two applications...
Let me explain (from experience b'coz that's how we are using it),
1. 1 Per App Plan give you license for 2 Canvas Apps.
2. These 2 licenses can be assigned to 2 different users for 1 App.
3. You buy these licenses from the Office Admin Portal as usual.
4. In the Power Apps Admin Centre, you assign these licenses to the Environment where your App is located.

5. Go to the settings for that App and turn on Pass Assignment.

6. Share the App with the Users.