Welcome to the forum! There are four nodes in Audulus that Respond to incoming MIDI messages. The most important of these is the keyboard node. It receives MIDI note-on messages and outputs the note frequency and a gate that is proportional to the note velocity. You can select Omni to receive MIDI on any channel or select a specific channel from 1 to 16. It supports single note legato as well as polyphony up to 16 notes. There is also a pitch bend node and knobs and triggers can also receive MIDI messages.
You should be able to send MIDI from any compatible device to either the iPad or Mac. For a DAW like Renoise the challenge is getting MIDI from the app to either the iPad or another stand-alone Mac app. There is an AU available for the macOS version of Audulus although it uses a pretty old version of the code.
I’m not familiar with Renoise but it might be possible to send MIDI to the iPad using a network MIDI connection and to the stand-alone version of Audulus using an IAC MIDI port. At least I have been successful using this approach with Ableton Live. Another option for the iPad is an app called midimux. It has a small server that runs on the Mac and uses the iPad lightning connection to send midi to and from the Mac to the iPad.