I think your computer is defaulting to the integrated intel gpu happens with me on my alienware i also have the 650m. So far only way to use the enb is to use the injector version not the wrapper.
I dont know what the big deal is with these custom races all you have to do is type is player.setstage DLC1VampireBaseIntro 15 to proceed past Garan and his stinking immortal check and get on with the quest its what i did and it worked fine for me.