FYI - everyone has to mail in their application. There is no online option for family class.
How quickly it's received depends on what method you use to deliver it and where you send it from. Faster by courier - slower by regular post. Faster from Canada - slower from oustide of Canada. It takes a couple of months for IRCC to acknolwedge the application has been received from the time they get it.
I sent my application via Xpresspost (Canada Post) and it was received at CPC Sydney in 3 business days. I was able to link my application to my account on the day I received AOR. It only took one try!