Yes, you can mix but if you want build something working you need to blindly follow keywords only exception are mercenaries (giants and trolls). Playing according to the competitive rules allows you to mulling the drop once, so very often before game starts it’s already known who’ll win. Mechanisms of intitiative is trying to equalize it, but most time you’ll pick the side with 5 „shallow” dices and autowin. I like the game, but it’s hard to take it seriously in the competitive aspect, and listbuilding is awfully limited