i honestly think I'm a bit of a combination. I'll start writing an idea with a basic idea for the plot, but not 100 percent sure where i want to go with it, trying to create an idea of the ending. as i keep writing, even while not completely sure how it ends, i get to know the characters better, and come up with more ideas for their backstories, which effect their futures, and ideas for how that's going to go, and as they come to me, i write down those plot points, and then end up having to figure out how to thread them together.
so perhaps i start by pantsing, and then plot more as I go. my MBTI is the architect, so i definitely prefer to have a plan, i freak out a bit if i don't know where things are going, but sometimes you just have to start to know what you're even working with. Once i have the characters fleshed out, i can design their futures. it's like how you can't start building until you open your tool shed and see what you have available to use, or what else you might need to get.