Can a super admin install themes and plugins exclusively on individual sites?

Sorry I forgot to mention that I am using WPMS 3.0.5.

Yes and no. You can have different themes and plugins for different sites — that is no problem. But…the themes and plugins you install are “available” to all sites in the network. That said, only the super-admin can choose a theme for a site and, as super-admin, you can choose to make plugin selection available or unavailable to the administrator of the site.

So yes — you can run totally different sites with completely different themes and plugins from one installation of WordPress. As far as sharing plugins, you can choose to block everyone but the super-admin from being able to see, activate, edit, etc plugins so the decision to “share” a plugins lies solely in your hands.

Themes yes.

Install the theme. DO NOT make it active sitewide. Go in to the Network admin (super admin) and edit the site. You can activate the theme JUST on that site.

Plugins is more complicated. You need a … plugin to do that.

PLUGIN MANAGMENT
* https://www.ads-software.com/extend/plugins/exclude-plugins/
* https://www.ads-software.com/extend/plugins/wpmu-plugin-stats/
* https://www.ads-software.com/extend/plugins/restrict-multisite-plugins/
* https://www.ads-software.com/extend/plugins/plugins-enabler/

Thank you so much, Ipstenu.

If those themes are not active sitewide, will the admins of each site see it or are they hidden?

No, they’re hidden to everyone per-site.

Even if you, Super Admin, goes to a specific site’s appearance menu, you will NOT see the non-active themes. You can only see them on the edit back end.

Thanks again!