Multisite Spammers & Other Questions

I’m new to administrating a Multisite Network, but I’m not new to administrating WordPress websites. On a normal wordpress website I would activate Akismet and disable registration. I don’t know what to do on a multisite network. I’ve installed Akismet on each site and it’s been doing a great-ish job at catching spammy comments. I don’t know what to do about spam registration and site creation. Are there any plugins for multisite that will take care of this network wide? I’m open to suggestions.

Also, is there a way to automate things on a multisite network? I install Jetpack, Akismet, and etc, can I activate and configure it network wide? If my network gets more than twenty members this will be a full time job.

Thanks