I'm thinking about redoing my story outline as well. I like one of my protagonists but not the other so much. And my conflict is alright but could be better. I'm thinking of making some changes too!

Pantsing is my preferred M.O., though I'm enjoying giving proper planning a try. Seems appropriate for a mystery novel.

If you're looking for pantsing advice, though, I can certainly share what I do.

I come up with a character that I'd like to write, as you have. Then, I think of a few other side character I'd like to see interact with the protagonist. Then a situation or conflict that would be amusing to throw them into. Then I write what happens...

...and that's pretty much it.

When I pants it, usually about halfway through, I begin to think about how to resolve everything now that I've put my protag in a real bind, and gradually work toward that resolution. I've written two novels (and almost all of my short stories) in this way. I did it with the short story about my protag.

I fully intend to start from the plot outline I've created here, and I'll definitely use the character prep, but if the characters pull me in a different direction as I write, I'll happily go with the flow. If my predetermined plot comes into conflict with where the characters need to go, I'll almost certainly follow what feels right for the characters.