My bet is the dark urge is just a way for you to play the "fuck you DM I'm gonna ruin you plan" kind character.
Which is kind refeshing but unltimately it makes you missing bunch of content because you are a murder hobo.
Eh you can kill everything in the game already. That's part of Larian's N+1 design. So you can do that with any character. This seems more like, if you want to experience the Dark Urge storyline, you can't meaninglessly kill everyone at the drop of a hat/when you first meet them, because there will be scripted experiences throughout the game with it. You might still end up killing them anyway, but you might not, and the fact they mention it having romances and stuff doesn't make it sound like a murderhobo route.
I both do and don't like this idea. What I like about it is that "you have the freedom to do anything!" from Larian was always a lie. If I take an N+1 action and there is no consequence/reactivity to it, it's pointless. They might as well not have that option. So that's good if they're offering some reactivity to being a murderhobo. But there are a lot of ways this could end up being retarded depending on how they write/execute it, we just won't know until we play through the whole game.