If you have questions, comment or experiences in Waterton Park in Canada, please post them in this section, although Glacier is the Focus, Waterton is the sister that has much to offer.
I've camped at the Goat lake and at snowshoe campgrounds as part of the Avion ridge loop (which you can do as a day hike, alternatively).
Goat lake is in a nice bowl and you often can spot a mountain goat or two on the cliffs above the lake. There are a couple of peaks you can hike up from this campsite (Avion ridge, Newman peak) following the hiker trail up the headwall at the end of the valley.
Snowshoe campground on the other hand, i'd not recommend as a destination unto itself. You can actually bike the trail as far as snowshoe campground, which might be interesting for some... but the site is in a forested valley with minimal views and the trail to that point is not very interesting. The Twin lakes campsite is pretty awesome and just a bit further afield (maybe an hour's hike away). It's a great site just below Kishinena peak, which is an easy scramble from the campground.
The Tamarack trail sounds like a great backpack. When are you planning on doing this? The reason I ask... the tamaracks (larches) must be awesome along this trail in mid to late September, so that'd be my vote for the best time of year.
Note that the through-hike starts from the Cameron Lake road (Rowe Lakes trailhead) and ends at Redrock Canyon road, so it's not actually a loop. You'd likely be able to hitch a ride back from Red rock canyon. Alternatively, you could pre-park a 2nd vehicle (or pre-park a bicycle for the driver to fetch your vehicle at the Rowe Lakes trailhead). It's a fun ride downhill all the way down Redrock road, but a bit of work to then get back up Cameron lake road to the other vehicle. Just an idea!