Yes, that damn old question again. And I can't believe I'm asking this question myself.
We all know what the answer is: Do what is right for you.
The problem is, what is right for me isn't always right, and sometimes it's outright wrong.
I'm mostly a pantser: I write by the seat of my pants. I like the way my characters take me places, show me new alternatives, and surprise me. I like how their decisions change the plot, and move it organically. All is good.
But there are times when I'm so frustrated with my characters I want to give up. The detours are getting ridiculous, and a 120K book turns into 180K, because the characters start to tell more stories, taking in more subplots, or moving the plot with more twists and turns than I'd like.
What to do? It sounds good in theory, but in reality, the writer (that's ME) has to rein it in somehow. A novel shouldn't be a runaway train. Of of these days (and soon) it should end.
Often, I'd try to do a very brief outline, nothing detailed at all, showing how I'd like the plot to go, toward some kind of a goal, or set pieces, or end points. They serve as the guideposts so I don't wander off somewhere and the story doesn't turn into a plotless mash.
I had one such outline written out for the last part of my WIP, and I thought it was pretty good.... until I started writing. Then suddenly the plot I outlined sounded cliched, melodramatic, and complicated. And my characters started to ask questions: "This doesn't make sense... why would I do that?" or "Where did I get that piece of information?" or "I'm not going to do this big info-dumping dialogue!" My characters are rebelling! And knowing myself, I realized I must listen to my characters, as they come to this point of the story. They know their stories, and they are telling me something.
My characters are telling me, they want this part of the plot more emotional and less dramatic. More resonance with the readers and less extravagant and climactic. At the very least, it should feel organic and not forced -- to be dramatic for dramatic's sake.
And I started to agree with them and ended up scrapping the outline and 2000 words. Granted, I didn't really like words. Still, that's a few hours of work I just threw out.
I just hope I'm doing the right thing. There are times when I have absolutely no confidence, especially when it comes to plot. What is too much? What is not enough? I have no idea. I can only listen to my characters and hope they are right, and I was wrong.