All I know is that you'll need a reference letter from your employer for AOS. All of the required documents will show up once you get into the process.
For me, I think it's the fastest way. I also submit a request in the webform, but they'd never returned to me. https://eservices.cic.gc.ca/ols/login.do?&app=epay&page=viewallreceipts&lang=en. Follow the step and initiate a refund in this website.
Tbh Montreal is quite inconsistent, I received my P2 on Thursday last week, and immediately received eCoPR the day after. But I'd bet my money on your receiving your eCoPR this week.
If the portal says your application is submitted, then it's submitted and currently in the hands of visa officers. AR email are just generic stuff, some have it, but others won't. I didn't receive any when I submitted mine. AOR is the more important one.