https://www.torontopearson.com/connecting.aspx

You can remain airside going through connections.

Time to go landslide, depends upon immigration. Before I got my residency it would take anything from 30 seconds to 45 mins. Though if you get to secondary it’s taken a friend almost 2 hours.

My concern is connecting to the US means confirming your bag normally, if you go out landslide then back through to the US area - not sure that’s what they expect.

I’m going to request a thread move to the AC forum given you are all on AC as I know people there will have done this connection type (Intl-YYZ-USA) and hopefully someone will know on the luggage point.