General WPMU Network Setup QA


could you please help me out with the right Network Setup?

When it comes to Plugins, should I activate them for the whole network? You have a lot of plugins that are usefull to administer a Network but these are not good if a user sees them. What is the best way to proceed?

Can I globally hide the plugin section at all, so that endusers just see specific navigation?

Do you have a general recommendation guide for a Network-Setup?

Goal: For our small agency customers we do not want to setup single Worpdress-Installations anymore but work with a network. We want to reduce costs to manage a lot of single installations of small customers.