20 gig? I've had a couple of 30 meg updates. And I don't have unlimited data.
And your questions are answered in threads created specifically to answer those questions.
However, when you move to steam and re-install they will auto subscribe you to the base content and you will DL all of that. You then have to unsubscribe from all the base content for it to be removed from your computer. There is no way I am aware of to unsubscribe from the content pre-emptively.
No worries thank you so muchYes you can, but for singel-player and Devmode only.