I always run water from my fresh water tank and use the on-board water pump. No danger of over pressure on the pipes that way, AND never under pressure either. It's always the same, regardless of what the campground has. I never leave the on-shore water spigot turned on and use it that way. The only time shore water is turned on, is to fill the fresh water tank.
That's how I do it.
Besides, an external water pump will not aid in creating more pressure or providing more water. The source of the water can only spit out so much pressure. If you attempt to suck more out than what is available, you'll rob water from other campers, possibly do some damage to the campground pumps and possibly put more pressure on the campground pipes (a reverse pressure).
Who you are right now is a sum total off all you use to be.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually