If you detail both the foam and the wall board as an air barrier (acoustic sealant &/or duct mastic on the seams, 1-part foam on the edges) you don't gain anything with interior Tyvek. In zone 3 a layer of 6 mil poly on the interior of the wall would be a mistake, especially if there is brick/stone/stucco siding. The vapor-retardency of half-inch XPS is under 2 perms which still allows the wall cavity to dry toward the interior, but won't load up the sheathing quickly from interior moisture drives in winter. It's about rigth as-is. If you put poly in there it must dry toward the exterior, and in summer that just isn't happening much when the dew points are north of 70F, and you can end up with condensation on the poly inside the wall cavity sometimes in an air-conditioned house. With half-inch XPS the air conditioning continues to dry the wall assembly during those steamy hot periods, so the moisture is less likely to get ahead of the drying rate in summer.
Tyvek Attic Wrap has an integrated RB, which may be worthwhile in your rafter application if you go that route. Even high-density cathedral-ceiling batts are partially translucent to infra-red, and having a reflective layer on the exterior improves it's cooling season performance.
An alternative would be to dense-pack the rafters full depth with cellulose, and use only latex paint as an interior vapor retarder. This works in Atlanta as long as you're not running a humidifier and keeping it at 40% or higher in winter, but but not in cooler climates. See the table 3 on p.12 of
this document.
If you're leery of that, consider doing a 1" flash-spray of closed cell foam first (it doesn't have to be pretty or perfect, just full coverage on the roof deck), then dense-packing it or install full-depth high density batts, even if you have to compress them a bit. The flash of closed cell foam forms a non-wicking condensing surface in winter, that also is a ~2 perm vapor retarder. Even when the roof deck is below the dew point of the interior air it's rate of moisture accumulation thorugh the foam is pretty slow. But when spring comes, the high vapor-pressure of the sun-heated roof deck dries the roof deck through the foam into the (moisture tolerant) cellulose, which stays pretty much at room-humidity as long as you don't put poly or foil or vinyl on the inside, only latex paint. In summer the air-conditioning dries it out further, and the foam limits the rate at which sun-baked roofing after a rain can drive moisture into the cavity, and condensation on the gypsum is avoided.
The flash-foam will also be more air-tight than is readily achievable by a retrofit of interior Tyvek, if you be sure to spray it down over the soffits and onto the top plates of the framing too. Overall the cost of flash foam may even be cheaper than the material + labor for doing the Tyvek chute process meticulously too. Figure on about a $100/roofing square, or a buck a square foot. Then you can use either blown cellulose (recommended) or unfaced high-density batts to fill up the rest of the cavity, with only standard latex paint as an interior vapor retarder.
With ~ R6 of closed cell foam to the exterior of the fiber in an 11.5" cavity, (10.5" of cellulose or fiberglass) you'll have R38 in fiber, R6 in foam for R44 center-cavity, and the number of condensing-hours per winter at the foam/fiber interface will be much fewer than in the dense pack/roof-deck case. At 70F/35% RH the dew point is about 40F. The foam/fiber interface is at the ~86% point of the delta between room temp and exterior temp, so to hit 40F at interior surface of the foam it has to be below 35F outside, and it's only an issue if the AVERAGE temp stays that cold over several weeks to have problems in the fiber insulation. The mean January temp in Atlanta is about 40F, so the mean January temp at the flash-foam/fiber would be 44F, so you'll have PLENTY of margin with that approach.