The free plan has one fixed rule, an alert when there is no reply within 24 hours, and no alert for opens. A single open or click never sends a notification, so the extension settings have no switch for it.
Remember that an open alert rests on opens, which are not proof of reading. Opens by Apple Mail, a provider’s proxy or a scanner never fire one. And opens and clicks are recorded only in tracked copies: after your company switched tracking on, and only for recipients whose consent is recorded.