If you turn power match off it will use the power directly from the Kickr and not the pedals. In your case if you see 170 from the Kickr and ~158-160 from the pedals then the pedals are reading that much lower than the kickr at that power. Worth noting that it isn’t likely a straight 10-12 watt difference and that if you were doing 340 watts the difference will be different (not necessarily more or less - just different).
When you enable powermatch the power numbers you see in TrainerRoad will be from the pedals. I’m not sure I fully understand your question - but essentially the power recorded by TrainerRoad with powermatch on is your pedal’s power reading, not the kickr