1. No. Public Shared is a collation of shared files & folders. (eg: I share from several folders & drives. I also download to a different drive to default, not the OSX user account drive.) 2. Yes depending on your set up. (This is of course customisable as you wish.) 3. Not sure, I'll need to investigate.
Ah just realised you are a Mac user, Cool!
For question 2, may I ask how you wish to share files? Give an idea how you wish it organised. You can choose to share from almost any location on your computer. Same applies to download location. I think by default the download & shared location are generally the same for LW.