Enjoy your trip! I rode Vancouver to Edmonton once. It was about three hours late, but not a big deal. Once the ride goes over 24 hours, I figured the 12 hours after arrival is flexible time that can be dedicated to arriving late, as that is known to happen. The food is good, the bed was great (even in an open section), and the dome was pretty accessible, even in the park car. I probably did half my ride in the park car and never was asked to move along. The staff in the coffee shop under the park car was happy to make tea and work with the section passengers (as opposed to the Premier passengers). I think it might have to do with the shoulder season being a bit quieter. The train was only half full despite being 27 cars (included three deadhead sleepers mid-train).
Regarding baggage, I had two generous sized carry on bags. Neither was under 9" anything. Nobody said a word, and it all fit under my section bench. The restriction might come into play given the bedroom size, as there might be less space to store stuff. I would look up your bed room and see if a youtube video or pictorial shows a similar cabin. That might help you decide on luggage. Checked service is also available, not sure how early that must be arranged. Via uses a smaller baggage car that appears to be a combine of some sort.
The scenery is amazing, especially west of Hinton. If you have time upon arrival to Vancouver, stay for a few nights. It's easy to reach downtown from Pacific Central via Skytrain, which is clean and inexpensive. If you want a bargain hotel downtown, the Days Inn is clean and inexpensive most of the time. Some times it can get pricey when a convention comes to town or a cruise ship docks, but still probably the cheapest. If you want to splurge, look up Fairmont Hotels. The Hotel Vancouver, right downtown, is a former CN hotel. It's beautiful. If you can make it to Victoria (the ferry ride is the best $17 you will spend in a long time), the Fairmont Empress is ex-Canadian Pacific.
Anyway I hope this helps. Enjoy the ride. Here is a link to some of my Canadian pics: https://flic.kr/s/aHsmuY22X7
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