I've been over on YouTube watching videos by other authors on how they notebook their stories and I've reached a conclusion. Notebooking is a very personal experience.
I watched some authors that left me exhausted with the things they did in their notebooks. I'd be like too tired to write anything if I copied what they did. But it works for them and that's what matters.
There were authors who used multiple notebooks. I have two notebooks for the Paladin League, soon to be three, but that's because I filled them, not because I need more than one at a time. The only exception to this is that I love my 9x12 artist sketchpad.
This is something I usually pull out before I actually start writing a story. I like the extra room I have, and I like the fact that there are no lines which means I can write anywhere. It's funny because once I have the big picture on the book, I don't use this notepad again unless there's another larger issue I need to resolve.
I'm thinking it's all a mind thing. My brain sees the bigger writing space, the lack of lines, and says, okay, we're thinking big picture. As opposed to my normal, smaller lined notebook where I brainstorm character information or what happens in the next scene.
Maybe it was the writers who are out there filming videos, but all of them did more work decorating their writing notebooks than I'll ever do. For me, it's about thinking, not about making it pretty. I've shared pictures here in the past. I sketch things out, I write messy, I write sideways if I need to, I'll add Post-it notes with other information that I jotted down. The only thing that matters to me is getting my brain to work.
My method would probably drive other authors crazy, but it works for me. That's what matters.
Just like with writing, do what works for you and leave the rest.