You mentioned a hill. The equation for water pressure change due to an elevation change is 0.43 psi per foot of elevation change. If you take a water line 50 feet down a hill, you will have 21.5 psi more pressure at the bottom of the hill than at the top. If you take a water line 50 feet up a hill, you will have 21.5 psi less pressure at the top that at the bottom. That is with no flow. With flow the pressure drop due to friction comes into play as well. You will have higher pressure when the valve at the end closes since there is no pressure drop due to flow. Putting the pressure regulator at the end point of use then will give you constant pressure at the use point whereas putting it upstream will give variable pressure at the end point as the flow rate changes.
My brother has a 2" water service to chicken houses. Water company put in a connection type that is push-in with an o-ring that forms the seal and the buried pvc pipe is supposed to be held in the joint just by having the pipe buried to keep it from sliding. All was good for several years until the pipe shifted in the ground in the winter one night and the pipe end moved out of the o-ring. A 2" pipe will leak a lot of water on the main line. The water was spraying onto the fence and the road -freezing on the road and making icicles on the fence. It was a winter wonderland. A few hundred thousand gallons. Good news is that our water company will adjust the bill if you have a major leak. There is a limit of one adjustment per year or maybe 5 years. I don't remember.
Our water company keeps raising the line pressure since the old lines are undersized and they need to push more water to more customers. The pressure setting on your water heater relief valve is 150 psi. Water pressure in the main line creeps up during the night when flow rates are lower. Your water pressure regulator will shut off bubble tight when new to control the pressure when you are not using any water. But over time, there will be wear on the sealing surface and your regulator will seep a little causing the pressure in your house to rise to the pressure in the main line at night. Then your water heater relief valve will start dribbling if the main line is above 150 psi. A solution is to install two pressure regulators in series. Set the first (upstream) one to the pressure you want. Set the second one to a higher pressure. The second one will always be wide open so the seats do not wear. Since it is set to a higher pressure than the first one, it will be wide open trying to get the pressure up, but can't since the first one is limiting the pressure. When the first one wears out and start leaking (and pressure on your side starts rising), the second one with good seals will then close down to regulate pressure. If you put a pressure gauge between the two, you can tell that the first one is leaking and replace it.
