hi Daniele,
The activity plan allows to define:
1. 'Task templates', which are details of what tasks should be performed in the visit or work ticket,and its associated information as notes and attachments.
2. Surveys that are to be completed in the visit or ticket
After creating an activity plan, you need to create a routing rule to determine which plans are valid for which accounts so that it could be proposed when a visit is created for that account.
In the Visit screen, there are two facets called Tasks and Surveys. If the "Assign Automatically" flag is checked, then those tasks and surveys are added to the visit via an asynchronous process that runs in the tenant every 7 minutes.
The mandatory flag is only used as an indicator and does not have a process implication at this point.
Hope this helps.
Regards,
Sebastine