Two- you are better off that 5psi, but at 30 you are barely in the money to make water. I've tried it at 25psi, and at that rate could only make about 30 gallons overnight.
I have a 110V pump that makes about 100psi. Its a simple setup where I can bypass the pump if city pressure is good or I get tired of the diaphragm pump racket. If I'm in a hurry I shut off the bypass and plug in the pump. Pumps like this Flojet Booster pump
will work nice, and run your make rate to over 20gph. Another great advantage of the booster pump is the RO reject rate for dissolved solids in the water goes way up over 98%, ie the membrane is more pollutant-efficient at higher pressures, in addition to making water faster.
You should still run the reject at about 2/3 of the input to keep the membrane well washed and long lived. You can make that adjustment if you have the flow meter set. If you have the capillary tube back pressure method it is not adjustable.