I never did make a 2nd user profile. I believe that's right, though. If they link to the same online OneDrive, they will download the same stuff from it - based on their respective OneDrive settings. I guess it applies only to the folders each one selects to sync (at the Account tab, Choose folders button). And one or both may choose to use Files On-Demand. Whatever one profile does to the shared folders will soon happen to the other (when it signs in, I guess). Whatever happens to common folders/files at the OneDrive site will soon happen to both profiles.
Before deleting a corrupt profile, I'd want to be sure at least one Administrator profile still will exist. I've seen threads in which it is really tough &/or impossible to recover a usable computer without one - except with a clean install.