Hello dassu10,
I believe the 2000 concurrent session estimate is based on the Hardware appliance & may differ on the VM & AMI as they can have different "hardware" specifications. If you use the recommended settings (mainly switching the appliance to use 16 GB of RAM) it should be able to handle similar loads. We do not have any specific estimates for AMI/VM.
As for seeing who is logged in, as a Global Admin (super or any other user with this privilege) you can click Sessions > Manage Sessions to see a list of currently logged in users along with some information about their session. Here we have main 2 options for managing the session: You can force the user to re-authenticate or you can completely log the user out and kill their entire session.
There are also options to force recording or disconnect an active connection to a device.
Here is a screenshot of this page for reference:
Red = Force re-authentication (current connections & session will be hidden from user and paused until re-authenticated)
Orange = Log out (also kills all connections & the session)
Green = Force start recording for this connection
Blue = Disconnect this connection
Hope this helps,
-Christian