I use the iPad with AUM hosting AUv3 effects with the PX5 as the soundcard. Picutred is the 4 channels of the PX5 being processed with inserts on each channel. Parameters for delay and reverb are controlled from the Digitone. The PX5 can also be setup so that, when a channel’s FX Sends are set to ‘EXT’, the audio is sent to audio channels 9+10 in the iPad and can be returned to one of the other channels on the mixer (logically, the A channel on the far left). It’s easy, hassle-free, and gives me access to a boat load of high quality effects.
I this setup, the far right channel is my Digitakt. I am sending its signal as a sidechain source to each instance of Fabfilter Pro C2 so I can sidechain the other elements passing through the mixer. This is running an a 2018 iPad Pro and consumes about %35 CPU. If the iPad crashes for whatever reason I can just flip the switch on the PX5 to ‘Line’ from ‘USB’ while I reboot the app or iPad (or just carry on without processing if I really needed to hobble through a set).