The game doesn't make a "friend or foe" decision for you, whatever race, class and build you've taken. Your today's enemies could be your tomorrow's allies, and vice versa.
You cannot subclass light elven class being dark elf and vice versa. Also if you SOE near Dark Elven Village being light elf, you end up in Light Elven Village, and vice versa. But that's pretty much it.
1)What class developement trees are available to you at the start.
You can't for example become a Warcryer if you start as a Human Fighter.
2)What classes are available to you when you are able to subclass.
The two elven races cannot sub-class each other for example. Also no-one can subclass a Overlord or Warsmith.
Pretty much everything else is left up to you. (Who you party or clan with or even where you hunt.)