Can project managers access all employee data?

If you want the project managers to be able to view all reports and enter/edit the entries for all assigned employees, it is possible. You can achieve this by customizing the security permissions for the project manager. Check CORE Help Center for details. In particular, you should check the Reports option (making sure that you also check the Allow read option under it) and the Time Entry option (making sure to check the Allow access to entries of all employees option under it) on the Customize Profile > Screens tab.