I'm running into this problem, too. Airdrop is interfering with my existing file workflows and I cannot get it out of the way. I use Airdrop for files that I need before they are available on iCloud. I put a lot of files that land in Downloads into iCloud using Hazel, so Airdrop can cause duplicates that hazel will try to import both into iCloud ( e.g. Photos library ).
I might have to change where files download to from Downloads to another folder to fix this.