The steepest grade will be on the Tofino leg. Port Alberni to Uclelit (sp?) has a steep downgrade - curvy as well.
Next major downgrade is Hwy 5 Merritt to Hope. After the summit there is a long grade. But it is divided highway. Hwy 1 along the Frasier River does not have grades like this, but it is longer and curvier. And 2 lane south of Cache Creek.
Further east is Rogers Pass on Hwy 1. There's a long steady grade from the Pass to Revelstoke. But there are good stops along the way where you can rest and hike a bit. And earlier on 1, there is Kickhorse Pass. The climb from Lake Louise to the pass is negligible, but the drop through Yoho Nat Park is long and steady. But you can stop to look at the railway loops, and several side trips to sights in the park. This is the main highway across the country, divided where space allows.
If instead you take the Parkway north to Jasper, there is a long gradual drop from the Athabascan glacier to Jasper. Passes and grades west from Jasper to Hwy 5, and south to Kamloops are minor. Traffic is also lighter than on Hwy 1 through Yoho and Rogers.
