My notebook system or set up (the set of notebooks I use and carry every single day) consists of a Travelers Notebook, two A5 hardcover notebooks and a pocket sized one.
The Travelers Notebook always have two lined refills in it, and I use it for my daily journaling, or long form writing when I carry as few things with me as possible. The only accessory I own for it is their excellent pen holder. But I only use it when the Travelers Notebook is the only stationary thing I carry.
My pocket sized notebook is currently a blue Nock.co notebook, and historically I have been a Field Notes user. But I finally got fed up with their paper quality. I use it for shopping lists, keeping track of hours I work etc. The basic rule for what I write in it is stuff I need to reference when I’m out, or stuff I felt like I had to remember when I was out.
My two A5 notebooks are usually Leuchtturm1917; lined and the bullet journal version. But I’m currently using a dot grid Rhodia Webnotebook instead of the Bullet Journal because I tested the Webbie out, and I have a rule against having notebooks I just tested a few pages in laying around in my home office.
The lined on are used for long form writing, like this article for example. And the dot grid are using to manage tasks. Think of it like the bastard child of bullet journal and the dash plus system.