Each device server is multi-threaded with the default of 20 threads so it can discover 20 devices at the same time and the application server will process them in a serial fashion. The default is under system admin - device servers. Each device server can process 20 threads so if you had 5 you can discover 100 devices at the same time. Voyence is multi-threaded.
You do not need to run 2 separate jobs for the 2 devices.