The Stream, Reminders and Feedback tabs all work identically to those on a Listing Record in Rex. Check out the help documentation there for a better understanding of how to operate these features.
On the stream you'll be able to record any notes and interactions you have with the project and any of its related contacts from the top level.
Any reminders and/or tracks you need to set yourself and action can be managed from the Reminders tab.
Depending on the developer’s requirements and your method of operation, you can store project related feedback from the Project, Project Stage and/or the Listing level in Rex. Any feedback you need to capture from for the project can be stored on the Feedback tab.