Hi, usually, if Medical Exam is uncomplicated, the panel physician sends results to IRCC via E-Medical electronic system (if this system is used in their office) within 5-10 days after your visit. Then, an additional 7 days for IRCC to post on your online application that you have passed. Sometimes IRCC posts when the medical results were received on your online account, as "received", but in many cases, like in mine, IRCC just updates your account that you have "passed Medical Exam" (if you did).
Background check may begin at the same time Medical Exam request happens or just right after exam was requested.