"I'm interested in knowing what you think about the way most PPLs seem to be taught about cruise power settings"
2300rpm
Regarding fuel flow, nobody had much idea. One was taught to look in the tech log ; there would be a figure written down by the previous pilot, e.g. "3.5hrs" and that was your remaining fuel.
And so one went flying....
Personally, I used to always fill up, except when flying with an instructor and then I would hand him control if we ran out. Only once or twice I refused to fly and insisted on going to the pumps.
Now I fly a plane with a Shadin flowmeter, accurate to 2% and checked at every fill-up, and it's a revelation.
I don't think there is any way to know the flow rate of a particular 30 year old aircraft because the prop fitted may not be the correct type, so setting an RPM will not give a known fuel flow.
I flew a PA29-161 which would do 103kt ias, and another one which would do 95kt ias, both at 2300. That is a difference in engine power of about 15%. It is a difference in fuel flow of 15% but that's true only at peak EGT or LOP. These planes were always flown full-rich. Nobody ever found out why. It could have been just the revcounters.
The only way to do it properly is to fit a temporary flowmeter and do measurements. Has anybody done that?
Presently, I set a chosen power setting, 2300/23"/10.5GPH. This gives me a point LOP, about 65% and I leave it there. With proper navigation, there is no need to fly a specific precise airspeed.
FD is absolutely right about headwinds and tailwinds, but the relationship is complex. One wouldn't fly at max cruise into any headwind, and one wouldn't fly at Vbg into any tailwind. One could produce a graph of optimal power settings, but only if a flowmeter was available.