Is it possible to view a team member's activities without overlay in My Schedule of CRM Online?
Disable Calendar Sharing by removing Field-Level Security (FLS) permission to the CALENDAR_SHARE_RECENT_ITEMS_vod field on the Preference_vod object.
If a team member's Territories are below the manager's Territory, the manager is able to view activities by selecting View displayed in the top right of My Schedule. Only one user's activities display in the calendar at a time without overlay.
CRM Help Documentation: N/A