Chrome Management has become a lot more functional recently. Originally this functionality was only available to Chrome devices like the Chromebook but it seems they've opened it up to any device with the Chrome browser installed.
For better control over which Apps and Extensions can be installed in your Google Apps network you can "Force Install", restrict, recommend and block which Apps and Extensions you want you users to have access to based on the OU they're under.
You can manage Chrome extensions through your Google Admin Console OU settings under:
- Device Management > Chrome > User Settings > Apps and Extensions
You might also find the "User Experience" and "Content" sections useful.