RunnerTypes are either "BatchFile" or "PowerShell". BatchFile is legacy and I wouldn't recommend using it.
Status is a comma-separated filter. When omitted it defaults to including all "Succeeded", "PartiallySucceeded", and "Failed" builds. You can override it to any subset of these.
If NotificationAddress is omitted then there is no deployment success or failure email sent. If the diagnostic switches have been enabled in the configuration file the contents of the email will be available in the Application event log.
RetainBuild is not a filter. If omitted nothing happens. If it is set to True and a deployment is successful then the build in TFS is marked as "Keep Indefinitely" so that the retention policy doesn't delete it. If it is set to False and deployment is successful
then the Keep Indefinitely flag is cleared allowing the retention policy to delete the build as per the usual schedule.
The sample DeploymentMappings.xml file and the source code are the only real documentation at the moment. I will look into setting up a wiki.