On QF20 (MNL-SYD) in J you will not get PJs (unless they have changed it in the last few months), but will get an amenities kit. As has already been said, it is a 767 with Dreamtime seats. On the plus side, it is the 25 J seat config 767 which means that the 'A' seats in J are by themselves - the config is 1-2-2, so if you are contemplating the flight on QF20 and you have enough status, request 1a, 2a, 3a, 4a etc.
I have flown MEL-MNL and MNL-MEL via SYD(QF/QF), SIN(QF/SQ) and HKG(QF/CX and CX/CX) and my preference is SYD, HKG then SIN in order. A direct flight (if one were available on OW from/to MEL) would be preferable to all of those options IMO - even if it were a 737!.
Via SIN will add the greatest amount to your travel time (at time I calculated it was about an hour extra I think (based on MEL rather than SYD)) Also, CX and KA have a number of flights daily HKG-MNL and if you are a OW earner, that will give you better timetable options than via SIN. I do not know of any CX MNL-SIN flight unless you go via HKG (OW timetable tool doesnt list any direct flights) in which case you might as well pick up a QF or CX flight to SYD from HKG and save the hassles at SIN - otherwise, you could travel on a non-OW carrier (SQ or PH both fly mulitple flights per day MNL-SIN).