The allowance on Jetstar is weight based, so number of bags doesn't matter, just the total weight - you can check multiple bags with Jetstar

As per https://www.qantas.com/au/en/travel-...d-baggage.html , the domestic baggage allowance on Qantas for ADL-HBA is 1 piece of max 23kg per person in economy class. and 2 pieces pf max 32Kg per piece in business class.

If you hold Sapphire status then it would be 2 pieces
If you hold Emerald status, then 2 pieces in economy class and 3 pieces in business class

Is the ADL-HBA a standalone booking or part of a larger itinerary?