Multi-DB for BuddyPress Needed or default ok?

hi there,
i am just setting up a buddypress site. not a multisite (not more than one wordpress install if i got the terminology right).
1) is a buddypress theme site considered a multi site?

2)do i need to setup multiDB plugin if i expect to grow into a medium traffic social network community?

3) right now i have installed the buddypress compatible theme and buddypress plugin and settings configured. since i joined wpmu i discovered that i can anticipate future traffic and do this multidb. is it TOO LATE for me as i have already setup the buddypress plugin and theme? (site not launched yet etc). can i still do it?

4) is there any issues if i have plans to go with W3 Total Cache in the future with CDN integration if i do the multiDB plugin?

5) i have a vps account. all the DB created will be under my cpanel of that account right. it wont overflow into or need for me to create another cpanel account?

thank you