Since you are on one ticket and both of your flights are marketed by WestJet, the WestJet US to Asia baggage fee schedule will apply. Given WS does not seem to publish this, but does publish a "catch all" $40 at check in for the first bag on itineraries departing the US, I would expect to pay for bags.

Since you are checking in with Delta, Delta may (and I believe likely will) apply their first checked bag fee waivers for medallion members traveling internationally. As another poster pointed out, do NOT expect a DL credit card to get you a free checked bag in this case.

Given that you have a 13 hour overnight layover in YYZ, Delta will make you reclaim your bag in YYZ and re-check it with KE the next day. I'm not sure whether KE will charge you again, but my bet is that since your connection is under 24 hours they will not.