I got the mid-line Erlax. Had to thin the kitchen cabinet paint ( SW Emerald) a bit more than spec. I would go for the biggest if I were to do it again.
I have the semipro2
You will need to get the largest needle and nozzle size to do any water thinned paint plus thin it.
It does run good after that. Lacquers, thin polys and light oils/ stain works right out of the box.