JoeHans
Toggling the input echo selects all the hardware inputs. I'm using Maschine Mikro MKII and usually need the software input from Maschine VST.
All inputs includes virtual inputs such as the bundled Virtual Controller and LoopBe1. The Virtual controller because it is hard coded as a device, the latter because it is presented to SONAR as device. Plug-ins are different. For example, if ALL inputs were enabled, synth plug-ins that generate MIDI data would have a feedback loop setup. As it is, it is easy to create a feedback loop with MIDI virtual cables.