I don't know if you've been paying attention to the news lately, but airports are super busy and understaffed. Especially in Canada. When you're travelling to Greece this summer I highly recommend that you bring a carry-on and don't check any luggage. This will make the process so much easier. I also recommend that you check in online, and if you have TSA pre-check or nexus, use that for sure. Greece just changed the rules this year and you don't need to fill out a plf form, so you're all set on that end.