Did the Waterton, Banff, Lake Louise, Ice fields, Jasper trip last year.
Lots of Europeans fly to Calgary, rent RV and travel the area. You see lots of small to medium size rental motorhomes in the campgrounds and on the road.
Not many places to boondock in the area (that we saw, but some more experience persons may know of some out of the way spots).
Can use the Ice Fields Center lower parking lot for free (I think), we stayed at a campground nearby. Some of the parks have overflow parking for $10.00/night if they are full. Some don't. We did not do reservations and did not have a problem finding space but we always stopped early afternoon. At Banff we just made it before they filled.
Great bus service in the Banff area....pick you up in the campground. We just parked and used the buses there.
Lots of interesting places to hike.
Beautiful country...you will have a great time.