What is the best way to setup snapshot?

So I initially thought that backing up the main site would back everything up. I just found out that no, it isn't.

My first question I guess would be what does snapshot backup for each site? I guess I won't be needing to backup the themes and the plugins, what about pages and posts, custom post types etc... ?

Network settings? Network plugins?

And what if I select ''Do not include files'' what is backed up in that case?

I would like to backup to DropBox as well.

Thanks for your help,

Best regards,