My System setup details might give you some idea of the potential flexibility with Digiface/ES3 system:-
Digiface Adat Channel 1 - Hardware inputs used = 0 (1-8), Hardware Outputs used = 0 (1-8), Total mix routes 8 channels of VST’s into Reason via loopback facility from software inputs 1-8. Used for older VST’s not compatible with Reason or too CPU intensive to sit within Reason without affecting Reason performance. LoopBe1 used to control VST’s from within Reason via external instrument module.
Digiface Adat Channel 2 - Hardware inputs used = 8 (9-16) routes Eurorack audio outputs plus 4 hardware synth outputs into Digiface unit and then Reason via AD8200 Pre-amp unit. Hardware Outputs used = 8 (9-16) routes Audio/CV into ES3 unit
Digiface Adat Channel 3 - Hardware inputs used = 8 (17-24) routes Sonic Core Pulsar system into Reason via Total mix Loopback facility on hardware inputs. Hardware Outputs used = 0 (17-24)
Digiface Adat Channel 4 - Hardware inputs used = 0 (25-32), Hardware Output used = 2 of 8 (31 & 32) routed to main stereo outs.
As Hardware inputs, Software inputs and Hardware Outputs are not hardwired to each other you can set up very complex routing which can be changed to suit very easily.
I am looking to put another ES3 into system connected to Channel 1 Hardware Outputs for 8 additional Audio/CV channels. Could put another on Channel 3 and 4 if I needed to although limited to 6 outputs on Channel 4
Hope that helps.