Simple question, since I didnt get even automated response from support:

Will I be able to choose what server I will play on after purchase?

(as you would probably understand me - I dont want to buy one of the most expensive games only to learn I cant play with my friends)

Yes, one can either server. Depends where one can home and type of ISP you have, One might get some lag or not... Hard to say ATM

I believe it is. I also believe the devs confirmed a couple of months ago that you could switch between EU/US megaservers whenever you want.