Thanks for the suggestions ! After rethinking about it, I will stick to the Jasper-Banff area (there is a lot to do there and if I can save some time from going back and forth from National Parks, I will be able to do more backcountry hikes.
That’s fair, Waterton is pretty out of the way but also my favourite place on earth so I have to push it on everybody. What are you thinking for accommodations ? Things fill up fast because this is the busy season so if you are looking at hotels/hostels you should work on nailing down a few solid dates. Being spontaneous is alright too, some random homeless people camped in the trees behind my place for like 2 nights but I think 8-9 and somebody would have said something. I serve a lot of people who randomly end up at the hotel when they planned to be camping because the campsight filled up.