I would suggest CX for the fully flat bed, and for the CX service. I find the catering on CX excellent in J. Also Studio CX is fantastic.

Just be aware that QF is not selling F on QF 127 for a number of months. It will depend on the month that you are travelling in as to whether F will be offerered. Just because QF will sell you an F ticket on their website does not necessarily mean than F cabin will be available, as often on a dummy booking there will be a notation saying "Please note the segment from Sydney to Hong Kong will be in Business".

If no F class is offered on a 4 class 744, QF may decide to move some J passengers into the F cabin but provide J service. If they decide to do this, bear in mind that there are only 14 passengers that they could move into the F cabin. You will most likely need to be Platinum to be in with a chance of scoring an F seat in this scenario.