2nd: I see my IEM as a control over my playing. I do not expect to have the most monstrous mix on my IEM. I use it primarily to keep the focus on my playing. The mix and EQ I need for this differs to the tone I expect from my rig for FoH sounds.But you are right: the KPA's performance on high gain profiles with IEMs lacks a little bit for me. I do not blame the unit for this since I am not sure if it's me not being able to dial it in correctly.
I thought this at first, but later I realised a brittle tone in ears was affecting my playing. A great sound always makes you play better and cutting some top end and 4K, while boosting lower mids worked for my IEMs.
It is certainly not Kemper at fault and you just need to find what works personally with in ears.