Dennis @ PerfectForms
It is possible, and there are several different ways to accomplish it. It depends on how you are defining the recipients of the notifications. I will assume that you are taking emails from various fields to define Roles (or not using Roles and simply sending directly to those emails). In the behavior that sends the notification use a Simple Branch behavior object. Use a formula: Does submitter email = approver email? If True use a Notify object with 2 notifications. If False use a Notify object with 3 notifications.