At one time I used two of the standard RV pressure regulators together, since I had 2 of them, why not?
But then at one KOA park, the manager told us to make sure a regulator as their pressure was extremely high and could blow out our lines.
I really didn't know how effective my (by now older) regulators were, and we just got the new trailer. I decided to fill the fresh water tank and use the on-board pump, as the on-board pump would not spit out more pressure than what it was designed for, and no risk of blown pipes that way.
So, we've been doing it that ways ever since. Even with full hook-up sites, I fill the fresh water tank and pump from there. I'll leave the hose at the spigot as I have it on a real. And just stretch it over and fill the tank when it begins to get low. Been doing it this way for a few years now, and I have peace of mind the pressure is never too much for my trailer! AND, I don't have to buy another regulator.
This is something to consider? Noise of a water pump with the assurance you lines are "safe" or the quiet of garden hose with the uncertainty you lines may blow!