Hey, Congratulations on your visa approval.
I got my Letter of Introduction in my cic account. I feel you are travelling too early, they may rise questions regarding that, but again if your close family is in Canada it wont be an issue. I was asked to show my Approval letter from College and the officer confirmed my course, that’s all. The immigration was pretty smooth both in India and Canada. And yes, you can travel even if your course is fully online, make sure you get the supporting letter from your college.
Regarding the quarantine, yes you can stay with your family, but make sure you have a separate room with attached bathroom and you have all sorted for the 14 days, and make sure you really follow the Quarantine rules. And no, you don’t have to Quarantine in Vancouver, you directly reach Toronto and quarantine in your place.