Use Folders if and only if You Are Absolutely Certain
Yes, we do not recommend impose structure to the notes, structure grows themselves. However, if you are absolutely certain about the categorization, it shall not be a structure imposed, nor shall it impair your decision on where to put the note.
Creating such folders makes your life in the future easier. It’ll be much more doable to batch insert metadata to all notes in a certain folder. You may also want to merge or change the hierarchy of folders: no problem, since you kept the notes separable at the first place.