After catching up, I am gonna share my experiences:
APP FOUND ON ECAS BUT LATER DELETED...That happened to us in July 2018. We applied in June and soon after I could find my app and even had a file number (no X anywhere). However, after weeks of trying to link it, one day it simply went away...! My worst fear had become true, our app had been returned (for the third time!!!).
EXTENSION OF STAY (in CIC terms VISITOR RECORD): For the past years, I had been leaving and entering Canada (at least 5 times). Last time, it was the first time since I had gotten married to my Canadian-born husband. That was May 2018 and the border officer was not certain of allowing me in since we hadn't applied yet (had sent them twice by then) and had them returned same number of times). Anyways, in the end he allowed me back in not without insisting on me applying for the extension of the stay instead of leaving and re entering.
Now, if you have not received AOR yet, I do strongly suggest you apply for the VR of your status is about to expire.
Also, the status is NOT the same as the visa. They are two whole different things . The first one, TRV, allows you to present to any port of entry and request to be let into Canadian territory. Whereas the second, it allows and stipulates the conditions and length of your stay. It is highly recommended to always maintain a valid status, so if you have not received AOR yet and your status is about to expire, by all means do request a visitor record (extension of stay) .
Also, those coming from non-exempt countries, keep in mind that until ylu get your PR, you will still need a valid TRV to enter Canada.
When it comes to traveling while PR still being processed, even though it is not guaranteed, holding an OWP and also having a job. helps you prove to the border officers that you a) have a valid reason to enter Canada and b) will not be a burden since you are employed. Do note that it is not 100% certain... By law, only PR holders and Canadian citizens are always allowed entry, the rest it is left to the officers discretion.