I am wondering if there is a way to filter data coming into marking cloud from Sales Cloud. I ask because I do not want to import Accounts that dont have email address associated with them as these are taking up users in marketing cloud that I have to pay for but cant use.
Yes, but it's a bit limited.
Go to Contact Builder > Data Sources > Synchronised > open the SF configuration.
From there locate the object you want to limit and open it.
On left side of the menu you'll see the settings area for filtering out which records get synchronised. Click on Edit to make changes.