I can't help with everything and I'm sure someone more knowledgeable will be along soon to advise, but I think you're correct to say you need the previews, settings and presets. but the backups folder should contain more folders (named by date) that contain LR's routine backups.
You can delete as many as you're happy to loose, I'd suggest keeping a couple of the pre-update ones at the very least. I've always regarded deleting old backup folders as part of the routine housekeeping myself.
The ...corrupt... and ....temprepai... I suspect could be deleted. If you're in a hurry to get the space back, just copy them off somewhere else safe with a different name, delete them and see if anything gets broken. If it does have consequences, restore the folders, if not delete them at your leisure.