If you want a good feel for Prax, you need go no further than the Great Basin in the US. Prax really is the US Great Basin and Southwest (with elements of Wyoming and South Dakota).
Each desert is its own thing. And Prax and the Wastelands are definitely modelled on the Great Basin, the Chihuahuan, Sonoran, and Mojave deserts.
Whereas Pent is more like the rangeland in Wyoming and Montana:
For me the Pure Horse People have connections with Scythians, but the Praxians are sui generis. They ride bison, sable antelopes, high llamas, and impalas – they just are too different from any terrestrial people in core details.