If you configure an NX session, retain the NX server data.
Under NX > [Session Name] > Connections > Server, select the session type. Depending on the session type chosen, either the Unix Desktop, Windows Desktop or VNC Desktop setup pages are enabled to allow further configuration.
The IGEL setup pages for NX sessions are essentially an adapted graphical user interface for the NoMachine NX Client.
Further information regarding configuration (performance, services etc.) can be found in the original documentation provided by NoMachine: http://www.nomachine.com/documents.php