The Unas is an Unas. The playable races to start with will be: Human, Jaffa, Tok'ra, Unas, and Aturen. Other races may come in future books, but this is where we are starting. However, the Human race could be played as though they are from any of the planets, not just Earth.
Also, we are still in development of the class/classless system. We've got a lot of playtesting to do to figure out what direction we want to go.