When I put in my first drip system, I worried about pressure and pressure regulators. But then in a light bulb moment, I realized that, although the question seems complicated, the answer is pretty simple.
Toss all the regulators and build your system. If the pressure is too high and the whole system blows apart (that's actually never happened), turn down the faucet. If the pressure is too low and water doesn't get all the way to the end, split it up and make another system (or two).
In California, I watered 2 acres on 10 systems connected to 5 faucets. I added battery operated irrigation timers at the faucet end to turn water on and off on a schedule.
Here in Reno, I converted my sprinkler systems to drip when I took out the lawn. Once again, I was warned that it couldn't be done because the water pressure would be too high on such small systems. Simple solution: turn the water pressure down at the solenoid.
Hope this helps.
