Measure your gpm and psi
Two numbers decide your whole system. Both take five minutes.
Pressure (psi)
Screw a pressure gauge (about $10 at any hardware store) onto the outside faucet closest to the water meter. With every faucet and appliance in the house off, open it fully and read the gauge. That is your static pressure.
Flow (gpm)
Take the gauge off. With everything else off, time how long the same faucet takes to fill a 5 gallon bucket, wide open. Divide 300 by the seconds: 30 seconds is 10 gpm, 50 seconds is 6 gpm.
Which plan to pick
Pick the plan at or below your numbers: if you measured 10 gpm at 58 psi, use the 9 gpm at 55 psi plans. Never round up. A zone that asks for more water than the house can give will not pop up its last heads.