Beware the TW2 on Steam still uses add. DRM with a 3 activation limit.
What is the point of an activation limit? To me, it sounds like a "Shove it" declaration to everyone who purchases it.
That's it - there is no point. It's the Publisher's middle finger to the customer.
Even on Steam are not safe from 3rd party DRM and only time will tell if the remove it like e.g. Of Orcs and Men and quite some other games.
I fell into that trap lately with Disciples 3 Reincarnation which has a 3 activation limit also. Since them I am on paranoid mode again.
In the TW2 case the only Version that does not f+++ the customer, as trusteft said, is sold by GOG.