You have four choices.
1. The Whistler, Pemberton and Duffy Lake route. Very scenic, I've driven it just once as it is out of the way, narrow and windy (twisting and turning). You do not want to be in a rush.
2. Hwy 1 to Hope then the Fraser canyon. Scenic, slow going in places, but nice.
3. Hwy 1 to Hope then the Coqhihalla. This is the easiest route. 110kmh speed limit once north of Hope, a four to six lane mountainous freeway. I like the scenery on this route. I drive the Coquihalla close to weekly and still like it. Set your cruise and go. Depending on time of year, watch for freak snow storms on this road.
4. Hwy 1 to Hope, then HWY 3 to Penticton and then north on HWY97 through the Okanagan. Again a very beautiful drive though Manning Park onto Penticton, then head north through the Okanagan to the 'loops.
Time of year and interests should be a factor.
Will you be doing the drive in both directions? Alter the routes?