An interesting story, although the first part appears inconsequential (couldn't they start out as desert people, without cataclysms and seafaring?) and differences between the two races and plain humans aren't very clear.
To understand better the history of that world I suggest reading about Humans (or Lore of the lands). Because the story about arhorians kicks off after the humans came.
And abot second one, the difference will be seen when I'll post all the race descriptions. Right now I'm busy with history and events that happened in that world. To make that world "alive" I need to spend a lot of time thinking of how would the world develop. It's a little disorganized right now, but I'll make it's more appealing when I'll have free time.