Is there a way to set up lets say 20 identical blogs with the same configurations easily without having to install each on and configure each one ?
i'd say make a backup of the mysql database and the files of a clean and succesful install then 'restore' them to make a duplicate
Yes, what camzio said. Just remember that you'll have to go in and edit the domain name for each blog before it will work if you import a MySQL database from another blog.
It's in one of the settings tables for wordpress in the MySQL database. You have to change it there or you won't be able to login to your admin panel for that site.