Multisite create new sub-sites with certain settings

Hi everyone.
I would like to know if and how its possible to setup multisites with the following requirements.
– user registers from the http://www.example.com (got it working)
– subdomain is created, user.example.com (works)
– certain plugins must already be automatically set to active, including certain settings within them (don’t know how)
– a default theme must be set (don’t know how)
– a default page has to be preset (don’t know how, but it did install a test page like in a new WP install)
– restrict certain menu items in the administration (I know there’s a plugin for that but don’t know which to use), must also be set default when a new site is created

Thanks for any advice!