Well smart playlists are a pain in the performance-neck, deffo.
They are really “smart” though. That is they are created in realtime for every query. TO buffer them would greatly improve performance. I rencelty played a lil with smart playlists aka “all except 2-7 dirs”, which came down awkward, performance-wise.
A list with all the song IDs should suffice, shouldn’t it? 😉