1. Do we need a special administrator for SmartDocs?
No. You don’t need to have a separate full time person to administer SmartDocs as there are no hardware or software to be maintained explicitly. Your SAP Basis team will be able to manage the ABAP add-on just like any SAP component. If you have a Google Apps administrator that person can manage the application on Google Cloud for user management, Drive account assignment etc.
2. What routine admin tasks are needed?
Nothing specific. Depending on how your SAP attributes are synced with SmartDocs on Google Cloud, there might be a batch job in SAP that need to be scheduled. But that is about it.
3. How are user accounts managed on SmartDocs?
Access to users for Search on SmartDocs is based on user admin module running on Google Cloud. You can set this up to use Google IDs of the users if you are Google Apps customer. If not user accounts can be created with appropriate authorization modes and access ranges.