From my understanding each tribe will have different characteristics and thus certain fighting styles will take advantages of these characteristics, ie what works for the Kypiq may not work for the Dras or for the Neran. While any tribe can use any style some are just more geared towards that tribe and will be more effective.
That being said, if you truly want to be a great warrior I feel you may have to travel and learn more than one style or weapon form from the different tribes in the world. Once you learn these styles or moves, then you can combine them in the way you feel is more effective. I think it is a mixed approach not locking you to a single style. You can have a Kypiq attack, Dras block, and a Neran counter if you so desire.
I am looking forward to the release of more information but I feel that each tribe will have a different style attack. A Dras sword attack may be slightly different than a Neran sword attack. And since this game is Classless I would think could use any weapon you wish, though some may be more efficient than others, for example a small Kypiq will have trouble lifting and using a Brudvir Greatsword.
So what I plan on doing is traveling the world, picking up all the basic fighting techniques I can, see which ones work for me or that I like, then try to specialize those and weave them into the advanced training for my tribe.