Perhaps not in the cabin, but there's a world of difference between 18-20 hours, and 20-24 in the cockpit.The SQ 21 flight NYC-SIN is timed at 18:30.
I don't see much carry-on about safety with that flight.
I don't see much difference with the project-sunrise proposal except SQ ditched Y and F from the config.
Singair (and the vast majority of other airlines) make heavy crews by adding a captain and FO for 4 man. So, any equivalent flight by just about any other airline would be 2 captains, and 2 FOs.So the key question the next is: what crew does SQ use for that flight and how does it compare with what QF want to do? How many flight crew? How many cabin crew?
For additional comparison, how does QF crew the PER-LHR and rtn legs on the B787-9?
QF never carry more than one captain, and one FO. Additional crew are SOs. SOs are not take off or landing qualified, and are not allowed in the operating seats below FL200.