My dream is to be able to create my ideal notebook myself (since I was making a ton of books around this time last year and so on). However....it takes a LOT of thinking about what you want to use the book for! I honestly have 4-5 notebooks "on-going" at the moment, but they are all dedicated to different purposes. Maybe I don't have a single notebook "Ideal"... :)
I've tried a lot of different systems myself. At work I use a combination of daily checklist that I created for myself and the monthly momentum planner worksheet from productive flourishing. https://www.productiveflourishing.com/free-planners/ with blank notebook paper for meeting notes. Work stuff stays in my office, so I keep that totally separate. I have a sketchbook and a small notebook that I use to keep notes about video games that I am playing. So no, sometimes "one notebook for every purpose" is not realistic. The little bullet journal is just my everyday carry thing, sometimes things that go into it get transferred elsewhere once I have access to the correct system.