I bought the 200gallon per day pumped version last week as i'm only just starting out and dont need hugh quantities of water yet. My water going in is about 220ppm and like you i have lowish water pressure. The RO is giving me about 400lts every 24hr with good to bad water being about 1 to 3 which on a meter might make me cry when i get the bill lol. One thing is get some decent resin as the stuff supplied was crap, water coming out before DI was 9ppm and the supllied resin could only get it down to 7.
Personally as i'm producing into a tank in the garage i have 24hrs a day to produce what i need, if i was going straight into the van and had to produce the water just while the van was on the drive i dont think it would keep you going.