Originally Posted by ashill

D and E are by and large the same actual jetbridges. E is just a departures waiting area a level above the D departures waiting area; the E departures area is after clearing US customs and take-your-shoes-off security for flights to the US. (I think there are some gates that are only E and some that are only D, but that's immaterial.) All D and E gates feed into the same CBSA inspections area.

Pre-pandemic, D gates were segregated for international departures. Now D handles both domestic and international (non-US) departures, and pretty much all widebody flights go out of D. However since your flight is on a 737, in principle it could go out of YYC's gates (except E); I don't know how likely that is in practice, since I've never had a narrowbody international departure from YYC. As mentioned, no additional screening (they will need to see your incoming boarding pass -- if you're coming from some countries like Mexico you do need to undergo security screening, but passengers coming from the US do not). Just follow the signs. It's a long walk or silly electric shuttle bus ride to the ABC gates, but otherwise I quite like the Calgary airport for connecting (despite many complaints here). In fact, I want the exercise on a connection, and YYC certainly gives you plenty of options for long walks!

If you qualify, the WestJet lounge in the B gates is among the best airline lounges in North America, but it can have capacity issues. They have a good variety of food options. I don't know specifically about veg/vegan, but I suspect decent choices. In principle they take priority pass, but usually not in practice during prime international departure times due to capacity.