Pretty much go by what the recipe says.
For the Genoa Salami, it says to cure it for 72 hours, but don't let Ph drop below 5.1. Nothing about a Ph range. It's at 5.8 now
For Pepperoni, there is a range, the lower is tangier.
I guess everyone does it different.
For the tester, I use the Apera PH60s.