Multi Site Configeration

I am currently using multi sites and allow users to register and create subsites under my site.
IE: abc.com/sampleusersite

That works like a charm however I need to be able to restrict what those new users can do.

For example:
I want to restrict the user to creating only one page sites.
I want to be able to brand their dashboard
Change the options that they have
restrict the user from adding plugins or changing themes
and so on

I dont want to manually configure every new site and create users and such because that would take several hours per site. (Or network I assume?)

when a new user registers a site I want everything to be set for them by default.

correct me if Im wrong but If a user registers and sets up their site they are in a new network and therefor the admin settings in my network dont cover all other networks?