My generic rule of thumb, if you have to pay an entrance fee or for some other reason have to see the staff at the entrance, get in line.
The border between Waterton and Glacier, ten years ago when I went through the border, there was no separate bike lane. But things may have changed in ten years. As you can see, there was no waiting line to cross the border either.
Canadians did not mind if I took a photo, but on the American side they get upset about photos.
That day had some nasty hills.