Dropbox on both MacOS (Sierra, 10.12.6) and Windows10

I'm using Parallels Desktop v15.1.4 for Mac and I'm so confused....

(I realize that this is largely a Dropbox issue but the Dropbox people claim to know nothing about Parallels).

First, I guess, I don't know what I really have. On the Mac side, I have a favorite called "Dropbox." The the PC side, I have two favorites, "Dropbox (\\Mac) (B" and "Dropbox". The latter shows the Dropbox logo. It is not clear to me whether Dropbox is installed on both platforms or if one is sharing that of the other? That is, do I have two copies of every file saved on my hard drive? If there are two distinct folders, should I be able to find them both on the Mac side?

On the PC, should I be using drive B: for Dropbox? I think that the two favorites should have identical contents, right? But they don't - and both say that they are successfully syncing. Worse, if I go into Dropbox on the web, the list of files there is not identical to either of the Dropbox folders that I see on the PC. It has some files that are unique to each platform but it is missing others.

My instinct is to just uninstall Dropbox and start again. I just did a full TimeMachine backup from the Mac. But (1) I'm not sure under the circumstances whether the backup would truly contain everything from both platforms, (2) I'm not sure where to uninstall it - Mac/PC/Both, and (3) if it wasn't installed correctly the first time, then what is the proper strategy?

 

B above should be B: