Can Dropbox send specific files to other Internet users without syncing with my HDD?

Dropbox apparently presumes that files stored in its cloud are primary and that the same files stored on my computer are secondary or even superfluous.  My Dropbox account currently is overflowing with files that I do not want there, but it seems that deleting them from Dropbox will cause these files to also be deleted from my computer.  I do not want to use Dropbox in this manner.  Its capacity is far less than the space available on my computer's drives and therefore it cannot function as a comprehensive backup system.  I will use a NAS for this.

Can this application be used to transfer specific large files (and none others) from my computer to other people via the Internet?  Can privacy be ensured by using a password to limit read/ download access to the people who receive the password from me via email?  Can I remove files from Dropbox without removing them from my computer and stop files from automatically being uploaded to Dropbox?  How can these functions be accomplished?  I could find no information in the Dropbox help system to answer these queries.