I can have all my 4K movies in one folder called 4K Movies? They don't need to be in separate folder do they? The folder structure should be similar to zappiti I would think?
Using a 'flat folder' structure could lead to problems
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I've always followed the 'best practice' rules set by Kodi ... each video in its own folder. Also in that folder you should put all of the images (fanart, posters, ...) and an nfo file for that video. It makes management far easier.
There is plenty of information in the Kodi Wiki:
https://kodi.wiki/view/Naming_video_files/Movies