That was informative and lengthy way of confirming I'm on the right track with my choices so far...
Based on my testing, I can say that 15ish degrees initial seems to be good compromise for my purpose, with no hard starting issues and temps were only 4degF (~2degC) up from full manifold vacuum. Although I did not attempt to optimize dizzy vacuum advance amount when using manifold vacuum. (It may well have given too much advance?)
Lower temp switch seems to be the one to use. It was also interesting to note that in 60degF weather the coolant temp drops at least 10-15 degrees before getting to the rad. And the separately grounded Veglia gauge seemed to show accurate info.
One thing I'm curious though is your recommendation to use higher temp fan switch than thermostat, considering the temperature drop in the cooling pipes. It would seem to me that about the same temp or little lower than thermostat opening could be used, and it would still cycle the fan off when driving at highway.
I admit I still haven't looked what thermostat I have, as I want to do some other stuff once I let the coolant out. But eventually, I'll check this out.
By the way, I happened to test the other day one 160deg Robert Shaw thermostat against five 180degree ones with boiling water (212F). Curiously enough I found that stabilized at that temperature, the 160degree thermostat was fully open and all 180degree ones were open, but not fully.
So it could be interpreted that 160degree thermostat might help cooling with high temperatures compared to higher rated ones? It doesn't just open earlier, it opens further as the temps continue to go up.
So despite the possible increased wear out (and possibly increased power), it could help with cooling when temperatures rise way above thermostat degrees.