Sorry I'm stumbling across this thread a little late! My $0.02 ...
The properties you've booked in Montreal are all fine. One property you may wish to consider is
Humaniti which is part of Marriott's Autograph Collection. It's just a block away from the Westin and it's a new building. I haven't stayed at Humaniti myself; I'm usually at the Westin if I'm in that part of town. The suites in the Sheraton can be nice; I once got the Vice Presidential suite and I wished I could have stayed more then the 1 night I had booked! The lounge in the Sheraton is reasonably nice too as is the one in the Delta.
In Toronto, as others have pointed out, the Marriott Toronto City Centre is in the Rogers Centre (formerly SkyDome) and they have rooms that overlook the field. If the
Blue Jays are in town, it's an interesting way to watch the game. At the high end of the scale we have a Ritz Carlton (Toca restaurant is quite nice) as well as the St.Regis (formerly Trump International). We also have a W opening up on Bloor Street. This property used to be a Marriott but it was closed for a few years (I'm pretty sure Covid got in the way) and completely renovated into a W. This property isn't open right now but I think it will open in a few weeks. The Sheraton is one of the biggest hotels in Canada - the convention area below is massive! The lounge is up top and has a great view of City Hall and the rest of Toronto. The Sheraton is / will soon undergo a major renovation which I think will take a couple of years minimum to complete. The Westin Harbour Castle is a decent place to go, but it's bit tired in places.
I'll leave Vancouver properties to the YVR experts.
My favourite Westin there (across from the library) was rebranded to a Hilton so I'm a little too out of date in that town now!
As someone else commented though, if you're coming to Canada, you would do well to consider Banff. It's an easy drive to Banff from YYC and it's a corner of the world that's worth making the detour to visit. The traditional (& expensive!) place to stay is the
Fairmont Banff Springs but the
Rimrock a good choice as well. If you go to Banff, consider Yoho National Park and Jasper National Park as well.
Good luck! Enjoy your trip to our wonderful country!