Short answer
You decide. "Remove from History" only forgets the record on your Mac. "Delete Remote File" also deletes the object from your bucket.
Both actions are in the library, where deleting a remote file asks for confirmation first. You can also select several uploads there and delete their remote files in one go. The "…" menu next to each recent upload in the menu bar panel has a quick Delete as well.
Deleting a remote file breaks its link immediately (or once your CDN cache expires), which is handy when you shared the wrong file.