The way you're using the words is interesting, because I tend to think of those words very differently! Just looking at the words themselves, I'd think of myself as a "creator" because "artist" doesn't seem to fully encompass what I do -- I'm not just here to draw pretty pictures; I want to create a world and a story and bring it to life.
The way you seem to be using them is more a question of: "Do you directly control every part of your work? Or does your work seem to have a life of its own, outside of your control?"
I'm gonna be honest, I kinda disagree with the idea that in order for your characters or world to be fully developed and alive and real, they also have to be out of your control. That's certainly a valid way to work, but I think it's equally possible to have characters that will make their own choices, and as a creator who knows them near-perfectly, build your story with those choices as a part of it.
Instead of going, "and then they'll go do [X] -- oh!! my characters don't want to do that at all! how alive they are!" -- instead, you can also start that decision knowing "my character's deepest desire is [X], which pushes him in this direction; that's the way he would choose go, so that's what he'll do, which will put him in conflict with this other character whose fear of [X] will drive her to stop him."
You can certainly learn more about your character the more you work with them (I love the marble analogy), and they can develop in ways you didn't see from the outset, and you can certainly end up reworking the plot when you find an option that rings more true...... but in the moments when I'm happiest with my work, I rarely see myself as out-of-control, with my characters doing whatever they like. I see myself less like a biographer or parent, and more like a deity -- I love them, and I love growing closer to them, but ultimately I know what's in their hearts and I create a perfect plan for them based on that!