As you are on one ticket, the entire ticket follows CX's economy bag allowance, i. e., 30kg, which should be an integral part of your CX-160 e-ticket. As a oneworld emerald, you are entitled to 20kg extra per https://www.oneworld.com/travel-benefits#benefits as pointed out, since this ticket follows the "'weight' system." That's a total of 50kg, not 55kg. The 3pc part per https://www.cathaypacific.com/cx/en_...#OnMostFlights, on the other hand, is not an integral part of the ticket. However, since QF doesn't limit the number of pieces when using the "'weight' system," per https://www.qantas.com/au/en/travel-...gage%3Aen%3Ann, I don't see any reason why QF will not let you check 3 pcs as long as the total weight doesn't exceed 50kg and as long as no bag exceeds 32kg. QF's policy for domestic checked bag allowance doesn't apply since you are connecting to an int'l flight on the same ticket.

For carry-on, you have to follow QF's rule for the QF flight. Again, per https://www.qantas.com/au/en/travel-...age-%3Aen%3Ann, 7kg shouldn't be a problem.