I’ve been thinking more about this and because there is no way to only move the video previews to a different folder/drive because they are not separated by folder, but sit inside the metadata ‘bundle’ of each individual video item, I fear Plex devs may consider this too big of a change under the hood to actually implement. So I had an idea that would not require this but would still satisfy most of my desires in the above post, however not necessarily the desires of the OP’s post, so I decided I needed to post it in it’s own thread.
The idea is a setting to allow the video preview files to be auto-deleted after they reach a certain age so as to help limit the space they take up. I hope this would be significantly easier to implement. Here’s the thread for that if anyone reading this is interested in supporting it:
Auto-delete option for video preview [BIF] files based on age
