Finally managed to get Nlog working and have Nlog, Addictive Synth, and Sunrizer, all going at the same time along with a drum track and a piano in Cubasis. That seems like enough to work with.
The order the Apps are opened in seems to have an effect on audio priority on some occasions and so I’ve had to reboot them to get audio back on occasion. Once I finally got all three working it appeared to be reasonably stable.
In the inspector I set the output to Virtual midi with the appropriate channel set. In the synth receiving midi I set midi input to Cubasis where there was an option.
Haven’t discovered a program change option yet so having to set programs up remotely each time I boot the App.
Hope this helps someone.