There are some assumptions beneath your questions that are problematic. It would be rather like asking about post-WWII biker clubs in North America: did they use chains and knives when they fought or did they also use guns? What kind of drugs did they deal? The answer is that there was a tremendous amount of diversity among various groups over just the few decades of history, and many were/are non-violent and aren't involved with drugs. Generalizations are completely unfair.

When discussing cultural phenomena spanning several centuries and involving many different Germanic cultures, we cannot talk about monolithic beliefs or cultural practices. Compounding the problem was that berserkers figure into post-conversion Scandinavian-language literature (not in all Germanic literature) in ways that were certainly fanciful, and yet these references provide us with some of the most concrete ways to understand whatever these people may or may not have represented.

Throughout much of Europe, there was a core belief that people under special circumstances could transform into animals and that animals could transform into people. It was extremely rare to have an individual who believed that he himself could accomplish such a transformation. It was usually attributed to someone else, and more often than not, that "someone else" was in the next valley or in a previous decade, and the people describing him had not actually met him. In other words, the stories were folklore and not necessarily reflecting reality.

That said, were there warriors who actually believed that something of the nature of a bear (or wolf) took control over their bodies in the midst of battle frenzy? Perhaps, but who these individuals were, how they achieved this state, and how they behaved would almost certainly defy generalization. Too often, we project our literate (and therefore rather dogmatic) approach to spiritualism and mysticism into the past. Preliterate societies had a fluidity of belief and religious practice, so it is impossible to talk about "classes" of men who were berserkers, about who they might have worshipped, or about how they achieved whatever it is they actually achieved - as opposed to what they were alleged to have achieved.

At most, the phenomenon of the berserker must be understood through the imperfect lens of medieval references, each of which requires a great deal of source criticism before anything specific can be concluded - and those specifics cannot, then, be linked together to understand anything that would fit broad generalizations about various cultures from diverse places and spanning centuries.