A few plugins configuration

K so I have three questions;
First, using the MU Provisioning Plugin, can accounts be setup via the WHMCS admin panel or are they required to go through the cart itself?

Second, the Domain Mapping Plugin, how do people handle emails such as mymappeddomain.com, what if they want cooldude@mymappeddomain.com when its a domain mapped site. If it matters, we are on a VPS/cPanel server with WHM and we manage DNS.

Last Question: With mapped domains, I swear I read somewhere but can't find that the blogs.dir folder wasn't needed. Is this correct?