Is it possible to create a security group or access right that would provide you with access only to update the main Project Summary page and not be able to add team members or create tasks?
Release : All
The closest thing possible would be to restrict access down to not being able to add Team members, financial plans, but the users would still be able to create and add tasks. There is the ability to restrict it to just the view of the project properties page via instance and OBS level with access right: Project - View All Fields, but not with the edit as edit rights give the user other project manager rights as well. You could hide the tasks tab completely by inactivating it, but that would be for all users, and the users could still get to the Gantt to add/edit tasks.
Grant one of the below rights:
You can make the subpage(s) secure on the Project Properties page, and then provide view/edit rights as applicable to the users/group you want to be able to see the pages. This would help limit those who have access to view the project only to be able to update/see the properties page but not the subpages below it. Subpages also allow you to use to create display conditions as well. See more details at: Clarity Studio Object Views
Starting in Clarity 15.8, Secure Field Level Access allows you to make specific fields secure on the summary/details page secure. You can set up access based on what groups you want to be able to edit and view the fields. More details on this feature at: Secure Field Level Access