I think of MOCs as “topics” that naturally arrise through my notes. Let’s say I had notes for Kayaking, Snowboarding, Rooftop Parkour, Sky Diving, Hiking, and Rock Climbing all written months apart. I may later realize I should create a MOC called “Physical Activities” that captures all of them.
I try to utilize folders sparingly, but it’s a tough habit to break. The problem with folders is that they’re hierchal. I don’t want an “Physical Activities” folder, because that limits things. Perhaps I’ll have another MOC called “Fear of Heights” that also has Rooftop Parkour and Skydiving. It’s about creating maximum discoverability.
Tags I use to group things so I can find them with Dataview. For example, if I create a literature note, I’ll tag it “Source” and have a sub tag for type, like “Source/Newspaper”. As with MOCs, multiple tags can be used which helps with not seeing notes as a folder hierarchy.