Slab edge insulation, possible foam board over osb walls. – GreenBuildingAdvisor

I live in southern Kentucky and my house is pretty hard to heat and cool. It has a mix of 2×4 and 2×6 walls that have drywall insides and osb, vinyl siding on the outside. Its all sitting on an uninsulated slab that has an above grade stem wall on the outside perimiter of the slab thats roughly 4 inches above the slab. Ive decided that i want to install slab edge insulation by using 2 inch xps. Ive been considering installing 1inch xps (or whatever else would work), over the osb and taping all of the seams to get a good air seal. My windows are fairly new vinyl with a channel around the edge for siding. I can reinstall these windows over the foam board and retrim out the inside. Then resinstall vinyl siding or possibly new vinyl siding.

Im wanting some opinions on my plan. Some have told me that the foam board over the osb wouldnt be worth doing in my area and air sealing the osb boards would suffice. Any thoughts on this? Thanks!