Q. Is monitoring only performed on the endpoints used in the rule being applied?

No. Even if endpoints are not used for the rule, as long as monitoring details are linked to them, they will be monitored. Moreover, enabling/disabling monitoring means "Used/Not used to determine Live Status" instead of "Monitor/Not monitor." Therefore, even if it is disabled, monitoring will be performed and notifications will be sent when the monitoring status changes. To stop monitoring endpoints, cancel the link.