Travel time?

In fall 2015, we did GNP starting at Great Falls MT, we just dialed the St. Mary entrance into the Garmin and let it pick the route. Took us in through US89. From there we did GTTS road to Apgar/West Glacier. From there we dialed in Banff, and it took us west then north through Whitefish along US2/US93 to the Canadian border crossing at Roosville BC. It kept us on 93 north to Radium Hot Springs, and then we followed 93 through the mountains and wound up at Castle Junction. It was a nice drive, not a lot of traffic, and we could go at pretty much our own pace. From CJ, it was a back track down the TC (Canada 1) to Banff for a day/night, and then back north to Jasper NP with a stop at Lake Louise. It was worth the time to stop at Lake Louise just to see the color of the rock flour in the water. It's really picturesque. At that point, you can choose your route home. Like Wyoming/Montana/Colorado, the prairies in western Canada are notoriously windy. Heading in and back through the mountains would be my choice time permitting.
Also, if you choose this route, beware the bighorn sheep roaming the streets in Radium Hot Springs, and you might spot a moose by the side of the road along 93 between RHS and CJ. We did. :)