Opp. Plans Settings
The Opp. Plans tab allows Admins to control the Standalone behavior on Opportunities
Standalone View Options
The Standalone View Options allows Admins to enable Teams, Chatter and Files in the Standalone Application.
Result:
Miscellaneous
Allow ClosePlan deployment by Members
ClosePlan can be deployed only by Opportunity Owners and Users above in the hierarchy by default. If this option is enabled, any user with edit access will be able to deploy ClosePlan.
Surface the master Opportunity ClosePlan on child Opportunities
If enabled, Opportunities with a parent Opportunity will display the ClosePlan connected to the parent Opportunity.
To activate this feature, enter the API name (case sensitive) of the Lookup Field that represents the parent-child relationship between opportunities.
Up to four fields can be entered separated by a comma, with the order determining the priority.
Field Types can be Opportunity Lookup, Text or Text Formula field. (A field capable of holding the Opportunity ID).
Linked Opportunity ClosePlans can be unlinked from the Opportunity Widget or can be unlinked manually.
Note: Depending on Org settings, Users may or may not edit it or even view it if opportunity has sharing settings as private.