ExhibitPlus may not be using the .jabum folder, but ExhibitPlus does not do the image editing - that is taken care of by the Jalbum engine.
If you use any of the image-specific filters, the settings that you use will be stored in the .jalbum folder, so deleting it will delete those. You may not be using those filters now, but you may want to do so in the future.
okay, I hear ya. I'll leave the folder in place--now I have plenty of space, as I just got a new PC. Previously I was running out of room and so I didn't want to waste space with files I didn't need--all I see in the folder is a duplicate of the thumbs. I don't use any filters but who knows about the future.