Hi Hoot, Good to see you here!
I don't spend much time in Waterton...I always find there is too little time to do what I want in Glacier. That said, the times we have gone up we haven't hiked (except the first year Marc and I were there in September and I think we were doing the Bertha hike in the snow and it kept snowing harder so we turned back).
Our best memories of Waterton are probably just seeing bears along Red Rock Parkway. All black bears, but we have always seen some, one drive we saw 13 different bears. So if you're looking for wildlife photo ops, that would be a good bet. There are sometimes (sadly) habituated black bears in the townsite too.
I do know a lot of people love both the Crypt Lake and Carthew Alderson hikes...haven't done them though, and haven't done the boat ride there.
Honestly, I usually tell people that unless you have a LOT of time, to just stick to Glacier, there is so much to do and see. But it depends on what you're looking for and wanting to do...this probably wasn't helpful at all