I'll be transiting Canada so was looking for a bit of clarification.

My outbound is BWI-YYZ-HKG so I assume there is no immigration involved at YYZ since I'm just in transit.

My return is HKG-YYZ-BWI so I assume I do US pre-clearance in YYZ. I have GE but not Nexus, and I'm a US citizen. So I can just go to the Nexus line and show them the "CBP" sticker on my passport, then hand my forms to a live agent?