Look around at all the different types of planners and you will notice that some are meant for more intensive planning than others.
Pocket size weekly or monthly planners are geared toward planner users with low or minimal needs. Believe it or not I was a Low user once! In college (university to my European friends) all I needed my planner for was due dates and my work schedule. I used those Sierra Club planners with the week on one page and the other page full of a beautiful photograph. I didn't even use lists back then! I guess I didn't really have that much to remember. I got my classwork done and got to work on time, and that was all I really had to think about.
The vast majority of planners are for Medium users, which most people in the general population are. Horizontal weekly planners are simple and straightforward, and give you space to write what needs to be done each day without too much analysis. I graduated to Medium planner use in grad school, when my schedule was more complicated and I had more things due. I also had my thesis to write, my degree requirements to keep track of, and my research to plan. I used a horizontal weekly format in my personal size Filofax, and even though the day spaces were small they were all I needed at the time. I used tabbed sections to keep track of everything. It worked well for me then, but has never worked as well for me since.
After I had kids and moved overseas my life suddenly got a lot more complicated. I would say I'm a Medium-High planner user, as I suspect most moms (and anyone managing multiple people) are. I have to keep track of myself and everyone else in my family, make sure everyone gets where they are going on time, and with everything they need. I plan ahead for birthday parties, holidays, travel and events. I have to put all that information somewhere, and am constantly trying to figure out the best way to keep track of it all in a reasonably sized binder or combination of books.
There are several systems designed for the Medium-High planner user like the Organised Mum diaries (and countless other Mom planners) that help you keep track of each person in the family, budget, holidays etc. Uncalendar is geared toward Medium-High planner users and is useful for anyone keeping track of multiple things at once. I've heard students in nursing school (which is notoriously busy and stressful) love using Uncalendar planners.
I'm not truly a High level planner user. Those are the folks that have multiple meetings and scheduled events every day, clients and/or employees to keep track of, and multiple projects/ billables/ deliverables going on at once. I suspect most of these folks have moved over to Outlook, Google calendar or other digital ways to keep track of everything.
There are paper planner systems designed for the High level planner user. Franklin Covey is probably the most well-known and long-lived system for helping High level planner users to prioritize tasks and keep track of multiple things at once. Getting Things Done is a system I've heard a lot about but never tried myself, it is designed for very busy people too.
What about you? Would you consider yourself to be a Low, Medium, or High level planner user?