Audio flow - connections
Sonobus says it can use AU, VST & AAX plugins - so you can do it all without having to pipe anywhere else.
Wiring outputs to inputs is not easy even with Loopback. [Intercepting a set of inputs or outputs is a different task & much simpler to do].
There's a structure known as ReWire for inter-app audio comms, but I haven't used that in a long time.