Glacier can be very crowded, especially in July and August -- prime time there. If you want to drive the Going to the Sun Road and stop at Logan Pass to do some hiking (the Hidden Lake trail is awesome!), you need to be there very early in the morning, like before 8:00, to get a parking space. Really, anything along that road fills up pretty quickly in the mornings. Some say that waiting until late afternoon is a good time too, but then you are limited on how much time you have there before sunset. When we went, there was not one parking space available in the Logan Pass Visitor Center parking lot by 8:30 a.m.
The West Glacier KOA is a great place to stay! However, I see that they are already booking for 2021! It's possible they are already booked full for this year.
We had one very peaceful day in Glacier, away from the crowds at the Fish Creek picnic area. Very few people there, very quiet. Did a little fishing and a long hike along the shore of Lake MacDonald. Beautiful.
Whitewater rafting was one of our favorite activities in Glacier. Did that through Glacier Guides/Montana Rafting. Very fun!