I take the afternoon YEG-ORD pretty often. I have Nexus, so I get through security in ~2 minutes and through CBP in ~1. Generally, I'd suggest arriving at the airport 30 minutes before boarding time as long as you have your BP and don't need to check bags. They have a TV showing the estimated wait time to CBP (YEG is bag drop -> security -> CBP), and I've never seen it be more than 30 minutes (I've rarely seen it go above 15). FWIW, boarding tends not to start until T-35, but it's done pretty quickly.