Can the following be achieved via configuration of control variables in the out-of-the-box Lifecycle Manager...

Yes, disabling all notifications can be achieved via configuration of control variables in the out-of-the-box Lifecycle Manager (LCM) workflows. In SailPoint IdentityIQ, most workflows, including those in LCM, use control variables to manage various settings, such as whether notifications should be sent. By setting the appropriate control variable (e.g., disabling email notifications) within the workflow configuration, you can effectively suppress all notifications related to that workflow.

Therefore, the correct answer is A. Yes.