We've traveled all across Canada in our 30ft Class C towing a Saturn. On one tour we headed west thru Northern Ontario, Winnipeg, Regina, Calgary and then toured Banff, Lake Louise and Jasper. We then traveled over the Rockies to Vancouver. Headed south over the border then back ease from Seattle, Yellowstone, back over the Rockies and eventually home. A lot of big mountain passes. Used Cruise Control when I could but generally not when climbing the big ones. Used Tow mode on occasion.
Class C was on the Ford V10 chassis, no issues at all. We just took our time on the big climbs.
Make sure you book into appropriate RV parks ahead of time. Tunnel Mountain in Banff is great.