Hello,
If you add your blogs as sub-domains then, you'll need to set a redirect for your
http://troccoli.it/your_blogs to
http://yourblogs.troccoli.it so that,if a person browses
http://troccoli.it/yourblogs then he/she will be redirected to
http://your_blogs.troccoli.it .
And if in case you add them as a addon domain then, the sub-directories will get auto created for your blogs under public_html/folder and you'll just need to upload your blog data to their respective directories so that when any one browse your addon domains, they will get directly connected to your blogs.
Hope this will clear your doubts about sub-domains and addon domains..
Regards,
VConnor,
Support Team.