I like having a record of what I have finished and what I’m working on. It helps me to stay focused and not end up with too many WIPs or UFOs. I use a project sheet template I found for free online for each one and I keep them in a binder. I don’t keep up with them rigidly. I have finished five quilts since July and just today I updated the project sheets. I take photos of everything but none are printed. Some day I might put photos with each sheet but for now I’m okay with just having the digital photos. I also have a list (template downloaded from the same source) of my current works in progress to reference at a glance. As for future projects, I have a list of ideas and a couple of notebooks in which I sketch and brainstorm.
I think whether or not you keep a planner is a very personal thing. So is what kind of planner works for you.