My understanding is that since this journey is to/from North America, your normal allowance is 2 checked bags for free (do look at size/weight limitations per bag though). If you are Star Gold, you get an extra, 3rd bag for free. There shouldn't be any argument from CA at HKG check-in assuming this is all on one ticket and you're checking all the way through to YYZ. If on separate tickets and trying to interline, it's possible you could get an agent in HKG that will argue with you on the basis of cluelessness, but you'd be in the right to stand firm and insist.