I spent much of yesterday playing with a new story idea that came to me a couple of weeks ago. I don't think it will turn out to be novel-length, maybe novella-length, but I can never tell. It may explode. I'm not sure what I'd do with a novella. This doesn't seem like the sort of thing that will get much traction with most of the short fiction markets for fantasy, unless a themed anthology just happens to pop up at just the right time. It might just be something to put out as a cheap e-book to use as marketing and keep my name out there between releases. We'll see after I write it.
Developing a new story idea has reminded me of a question I get asked often by aspiring writers, whether I think of myself as plot-driven or character-driven. Get a bunch of authors together, and this discussion will often come up, with various value judgments about which is better implied in the discussion. Which is considered superior depends on which group you're talking to. Among romance authors, "character-driven" is generally considered better because it's supposedly deeper and more emotional, but in fantasy, science fiction and mystery, authors are praised for masterful plotting, with good characterization a bonus.
Really, though, I'm not sure it matters or if it's something that can be judged from the outside. The process doesn't necessarily show in the results, and a good genre novel needs to have both engaging characters and a well-developed plot (literary fiction has other expectations). When I hear from readers about my books, it's almost all about how much they love my characters, but my process is usually very plot-driven, where I first come up with the major events of the story and then create characters. There's a lot of back-and-forth, though, where I may have an idea of what the major plot problem will be, and then I'll think of the main cast of characters who'll be needed, and then I'll develop more of the plot, and then I'll flesh out the major characters, and then the specific steps of the plot develop based on who those characters are and the kinds of choices those people would make.
I do occasionally have a character in mind and fit a story around that person, but that's much more difficult to do. In the story I just started developing, I had the whole story outlined before I even started looking at who the characters were because it's the sort of thing where the types of characters were what mattered to the plot. The personalities came later, and I'm sure that will shape how I write the plot events, though it probably won't change the major events. If I do it right, it will yet again be a case of readers loving my characters, and they won't notice or care that the characters were secondary in the development of the story.
The bottom line is to write in a way that works for you and for the story you're telling without worrying about fitting into some mold or doing things in a way that's considered "better" by other writers. If you do it right, no one will be able to tell based on the results.