The Aux in are affected by the Output filter LoCut/HiCut, to me that make no sense to me..
I belive most people use the Locut/HiCut filter to shape the guitar sound and not the signal that are connected to Aux in.
I have used the Aux in to get a Aux send from the PA mixer and use the Phones output on the Kemper for in ear monitoring, and used the Aux in > Headphones as a mixer.
The problem is that the bass and drums from the aux in have the same Locut and HiCut as the guitar signal, and sounds thin..
I hope that this could be updated in the next Firmware so that the Aux in are routed after the LoCut/Hi Cut filter.