Does iCloud Drive duplicate files?

Hi all, I have constant problems with my hard drive storage running low due to massive amounts of "Other" - see photo. This means my work Outlook constantly has to go offline - I'm having to restart my computer twice a day now. I have tried to fix this in various ways but can't seem to - will have to reset and reinstall, I'm guessing.

In the meantime, I'm trying to free up as much storage as possible. When I run an app which frees up space (Cleaner One Pro), it keeps finding duplicate files: one in my Dropbox folder on the Desktop, the other on the iCloud Drive Desktop, which is a separate folder on my Desktop (see other photo). Can I delete one set of these? I don't understand what the point of storing stuff in the cloud is if it then takes up twice as much space on my hard drive, somehow?

Very confused and grateful for any help!