It seems from the research I have done that the 100% empirical answer is....
there is no 100% correct answer.
I replaced my factory radiator with a Wizard single pass radiator and am running a 170 deg thermostat (according to the gauge it opens about 172 or 173ish).
With the Wizard Rad and normal driving I see temps in the mid to upper 170s. Stop and go it will creep up to the low 190's.
With the factory setup and normal driving I would see temps in the mid to upper 170s. Stop and go would creep up to the low 200's.
I think, (YMMV), that for a well maintained, stock motored car, there is no incorrect answer. Either will work for you.
Apexes are a lot like relationships. So tough to get right, so easy to see where they went wrong.
The secret to a long life is ------- not dying.