Which layout templates are supported by the VSP Engine Tools? Can I use pre-defined ESRI ArcGIS Pro layout templates for prints in VSW applications?

All layout templates which you can configure in ArcGIS Pro or in VSP Designer are supported by the VSP Engine Tools (e.g. ISO A4 - A0, ANSI C-E, Letter, Tabloid, etc.). If you use ArcGIS Pro for your layout configuration and you do NOT import the layout template in VSP Designer to share your layout as Portal item, you can alternatively use the ArcGIS Pro Add-on VertiGIS Studio Printing Desktop Studio Layout Manager (licensed separately) to share the layout on your Portal. If you do NOT share a layout template with VSP Designer or VSP Desktop, necessary meta information is not available for using the layout template in VSW applications.