[ashlar]

Each time you are entering (or returning to) a media folder, the list will be refreshed, and Kodi will recreate these virtual items. The perf problem seems to be due to the additional database access for video version information query (if you uncheck the "as folder" option, no database access at all), I'll see if I can optimize the additional database access. You have many items in the list, right? It may help me debug the problem if you can share the debug log.

For the artworks, I designed a new media type for the movie version, so each movie version can have different artworks. I may be able to use the artworks from the movie item itself if the artworks for the movie version are empty, to "improve" user experience (I didn't add this as I thought using same artworks for all items in a folder looks boring).

As for the debug log, here it is, with movie versions as folders option active. In it, I enter the Movie section, Kodi "freezes" for 3-4 seconds, I enter a Movie with two versions (that happens immediately) and then I go back the whole list of movies and Kodi "freezes" for 1-2 seconds. Bear in mind I use a Ryzen 5 3600 with 16GB of RAM, performance shouldn't be a problem. Movies in the database are slightly less than 2500.

https://paste.kodi.tv/zuqokeguhu.kodi

As far as the artworks are concerned, I am not sure if I understand what you mean. Since Movie Versions are not created automatically as it happens for Movie Sets (when the relevant setting is activated), all movies have their own artwork lists. But when they become part of a movie with Movie Versions... that info is lost and you are only left with local artwork loading as an option. I don't see why you thought using the same artwork for all items would be involved, since pretty much all movies have multiple fanarts/posters/etc. available. But they are simply not accesible through Movie Versions. At least, that's what I'm experiencing.