Best to call the airline to find out before you book your ticket. This way, if you don't like the answer to your question, it is not recorded in your booking.

One would hope that your baggage allowance will be based on the 'piece' basis since your final destination is North America. But there appears to be a new 'rule' about baggage allowances that relates to the 'Most Significant Carrier' and on CX's website, it says to check with your local reservation office.

With the airlines constantly changing baggage allowances, it be best to check their website on their current guidelines before you book.