1. You can keep using Vuze while LW is installed. You don't need to move torrents. Note, using LW does not make you anonymous.

2. What is accessibe to other users is determined by what you designate as your "shared" directory. I believe you can have LW and Vuze save to the same directory. (Partial downloads in LW will be sent to Incomplete).

To avoid conflict you should designate one program to handle torrents (I recommemd Vuze, as LW is limited in its ability to handle torrents).