Came across this thread trying to answer another question.
But my 2 cents would be to run the Helix via 4 Cable Method (treating the KPA as an amp) You can google 4 cable method for an image of the cable routing.
4CM - Helix:
1. Guitar > Input,
2. Helix Send 1 (you can use any of the 4 FX Send/Return on the Helix) > Kemper Input
3. Kemper FX Loop Send > Helix Return 1
4. Helix Output > Kemper FX Loop Return
Place an FX LOOP block on the Helix preset.
Any FX Blocks placed before the FX LOOP block such as overdrives and distortion pedals will hit the front of the Kemper. And any FX blocks AFTER the FX Loop Block will be placed in the FX Loop of the Kemper.
You can also use Midi sent from the Helix to control the Kemper to switch Presets, FX on/off and Slots in Performance mode.