Angkor runs everywhere where Joomla runs, including Windows.
Angkor supports multilingual sites and RTL languages out of the box.
Angkor can format standard Joomla email. Angkor can format email from external extensions for which there is a plugin available for Angkor. Angkor cannot be used to format emails for external extensions such as JomSocial, or Community Builder, for which there is currently no plugin for Angkor available.
For CSS features typically supported by email programs, the following overview.