Refraction correction is a feature of some scopes where the pointing from the given RA/Dec is adjusted for atmospheric refraction so that, all else being equal, the target will be in the center of the field even though the light from it is being bent by the atmosphere (offsetting the apparent target location). This is most significant at "low" elevations. ACP can calculate the correction for refraction or leave that to the mount. I honestly don't know if the PlaneWave/PWI does atmospheric correction. It's likely an option in PWI. If yu have a choice, turn it off in PWI and let ACP do it. The correction in ACP takes into account the weather input (pressure and temperature) for a quite accurate calculation.

You're being really careful so I don't mind answering these sorts of questions. Thank you.