Your first two sections sound like a marketing quote from Kaseya. Yes it is that but it is a tool, someone still has to swing the hammer.
1. An agent can go on Linux, Mac, WIndows and mobile devices. What you can do through the agent depends on which device with Windows being the one that you can manipulate the most and mobile devices having very little management capability. Other devices that do not have agents can be monitored and if you go that far manipulated through SNMP or scripting. For example a DLINK router can't take an agent but can be seen by the system and monitored if SNMP is available or at least pinged to confirm it is present.
2. The dedicated server is located at your own office, not at the client site. Nothing is required at the client site like other solutions. This is great because the agents are still visible where ever they are. You can also go the SAS route where Kaseya hosts it for you.
3. No, no additional machine is required. You place and agent on the server and workstations only. No difference in cost for a server agent versus client agent.
4. All managed directly through Kaseya. The agent connects outbound from the customer machines back to your single Kaseya server. There are some options where you can designate one of the customer machines as a file source or as a machine that monitors SNMP, etc. But we typically just use one of the customer servers for this and don't have a separate server.
5. You have full awareness of any connected devices whether they are in the office or on the road.