Why would the pylon being in front or behind the prop make a meaningful difference? Whichever way, you're either sucking or blowing air through it at a speed proportional to the thrust you're trying to make?

Indeed front or behind does not make a lot of difference.
The cross section and shape of pylon is what matters.
The point of having the pylon in front is mainly to use foldable prop which lowers drag significantly when engine is not operating.