So the iConfig 'Audio Info' tab contains an 'Audio configuration' setting, which allows one to select the word length and sample rate of the audio subsystem. The iConnectMIDI4+ also has a similar feature, but IIRC, any 24-bit setting resulted in a significant limitation (channel count dropped IIRC). From the table in the iCA4+ manual, this limitation does not exist - I see no drawback to employing my preferred config of 44.1KHz/24-bit. Looks like the channel counts remain the same, as well as other parameters.
There is a statement in the manual about "This defaults to the CD- standard 16-bit/44100Hz setting to ensure compatibility with all iOS software." Is there a description anywhere of what software might be affected by changing to 44.1/24? Would the upper 8 bits not just be truncated (or preferentially dithered) into any SW that is limited to 44.1/16? And the upper 8 bits just set to 0b on the way out of such SW?