The Weed n Feed products typically act upon the foliage for broad leaf weeds and if the product contains a pre emergence for annual grasses, it puts a barrier layer in place that kills the germinating annual grass weeds from emerging. If you apply the Weed n Feed product before you aerate, you run the risk of breaking that barrier and or bringing weed seeds in the plug to the surface where it can go ahead and germinate.
If there is no annual grass control produts in the weed and feed, the order won't matter.
The more broad leaf weed surface you have the more uptake of the control product into the weeds should be expected. Mow the lawn if it needs it otherwise just apply your weed n feed product.
