Sadly, a lot of the roads close in to Vancouver (HWY 1)and up the Frazier River are heavily traveled , due to the expansion of the Alberta Oil Shale patch.
Hwy 5 has a "loop" (back and forth, actually) to Kamloops and Revelstoke that is very picturesque. The wildfires from recent years that incinerated Lytton and that area left a depressing spectre of devastation.
But you might want to head all the way up to Tofino. Tofino is a super charming villagey sort of place. If you like seafood, try the "boat" place, who's name I forget, but the food was great.
I seem to recall there's not many roads up the coast itself, but Egmont, Gibsons and the "Sunshine Coast" is low key and uncrowded, at least it used to be.
Watch your speed on open highways, there are often speed trap type setups in the center divides of main highways.