Both?
I guess if I had to pick one than the driving the narrative one would win. But I don't see how you could seperate the two.
Having choices doesn't mean that the choice that someone would prefer to make is valid.
I see the idea of "well choose the bad ending if you enjoyed it" type of commentary a lot, but the thing is I didn't consider myself to be choosing "the bad ending" but rather "the best ending available."
I'll state the unpopular opinion by stating that I don't think Shepard should be able to survive the Mass Effect trilogy. I never expected him to be able to to be perfectly honest. I'm perfectly okay with the player being put into the position of not being able to pick the ultimate optimal outcome. Virmire is another great example.
The Dark Ritual is a bit more interesting, because it lends itself a degree of uncertainty. I don't consider it necessarily an easy way out, especially if your character was at odds with Morrigan (and I think it's well executed if Morrigan loves you too).
So to that end, you make the choices based on the circumstances provided to you (and ideally, they do alter the narrative in some way), but I was referring to those that look at the outcomes and think "You know, I think this other option should be able to work too" simply because it plays out the way that they wanted.
Like the idea of refusing the Catalyst, where people often didn't just want the ability to refuse the Catalyst, but rather they wanted the ability to refuse the Catalyst and still win. In this sense, they wanted the narrative to go specifically how they wanted, which I don't feel must be necessary.