information on luggage check-in for 72 hour visa

We have a 12h transfert in Beijing, coming from Yangon, Myanmar, on Air China and leaving to Vancouver, Canada, on Air Canada. We want to take advantage of the stop to do a quick visit of the city. Is there any special procédures with the luggage since they will be registered in Yangon to be picked-up in Vancouver. Do we have to check-out and check-in luggage again or do we leave them with the Airlines as if we had stayed in the airport?

Thank you