1. Tableau Server Help - Set Up for Data-Driven Alerts.
Reference: In the section "Enable data-driven alerts (server-wide setting)", the documentation states: "By default, data-driven alerts are enabled."
Reference: In the section "Control data-driven alerts (site-level setting)", it states: "Go to a site's Settings page... Under Data-Driven Alerts, clear or select Let users create and receive data-driven alerts. By default, this option is selected."
Source: Salesforce, Tableau Server Help for Administrators. (This information is consistent across recent versions of Tableau Server documentation).
2. Tableau Server Help - tsm configuration set Options.
Reference: The documentation for the key dataAlerts.enabled specifies its default value is true.
Reference: The documentation for the key dataAlerts.checkIntervalInMinutes specifies its default value is 60. This confirms that option B does not change the default behavior and is not an enabling step.
Source: Salesforce, Tableau Server Help for Administrators.