Leaving a placeholder comment as I'm about to head out for a few hours. I have spent about two weeks in Jasper over the last two years, and have done both Skyline and Tonquin. They're amazing places, Tonquin is insanely muddy and buggy right now, but beautiful nonetheless. Skyline will be mostly snow free by the time you get there, so there's a bonus.
Okay, Creativity. If there are any cancellations on Skyline or Tonquin, go for it. Both are amazing experiences. There are a couple of great day hikes around there, too. Wilcox Pass is on the Icefields Parkway and is 100% a must if you are travelling to Banff from Jasper that way. Closer to Jasper, Bald Hills. Jasper is much more remote and much less touristy than Banff. You'll find far less people in the front or back country there - there are still tourists, for sure, but not as many. The backpacking is hard to beat in Jasper.
Thanks for the feedback ! I managed to get a camping spot at the Maccarib campground for Tonquin (1 night) ! Wilcox Pass is now on my to do list between Jasper & Banff.
One tip on Maccarib. As of three weeks ago both bridges to the campsite have been washed out. You'll have to cross a moving stream, it's not fast enough to sweep you off your feet but you will get wet if you don't have gaiters. Also keep going until you hit Amythyst Lake after you set up camp. It is so, so worth the extra handful of km.
Oh. I'm not planning on packing gaiters so wet foot it will be! I heard that Amythyst Lake was the highlight of the hike, their campground is still full though so I managed to get the closest one to it :)