Hi my brother is coming around today, so I thought I would add the second window to appconfig file, but it appears to be no longer working. oh dear it wont be a great experience for him without me to guide him along.
Get the new OBS Multiplatform software. Performs much better than the older OBS software and is more stable.If you're using extended mode, setup an OBS game capture in preview mode with encoding disabled. It'll give you a preview window on your desktop with very minimal performance hit, if any.
https://obsproject.com/