You would only get the metrics for the physical host, it would not automatically do anything for the guests. The typical install is: install on the VMs that are of interest from an application perspective, and optionally integrate with VCenter to get the VCenter perspective on the performance of the guests.
Typically you'll be interested in installing OneAgent on your virtual machines - therefore host units will count for 1000x size. In your case that's 100 physical 16GB * 10 virtual each = 1000 virtual machines with 1.6GB. That equals then to 1000 * 0.1 host unit = 100 host units.
If you install OA additionally on the physical box it'll be reported additionally as a physical host with 1 host unit each. However, I assume that this is a part of your ESXi VMware cluster - then you monitor these physical ESXi cluster nodes with ActiveGate - and that's for free and not consume additional host units to get insights how your nodes perform.