It more or less depends on how you set things up.
for multi-server you can use Virtual Servers –> where you can combined multiple servers (and services) into one account.
You can use it to:
- Combined Email server, Web Server, Database Server, and so on
- Combined multiple servers to provide the same services.
With option 2 it more or less randomly assigns you to one of the same services in the Virtual hosting plan.
I am personally generally a fan of option 1, not so much option 2 as it makes it more difficult to track down issues on the long run.
You can select a server or virtual server on each hosting plan, to which i prefer to create Virtual Server specific hosting plans (example web1, web2, web3 etc.) to keep things apart and easily track down issues if customers ever have it.