I would also include parts of Shropshire etc. in my question, as I gather that the county borders were not all static.
I understand that the administrative and legal base was at some point established at Ludlow castle. I would be particularly interested in what that entailed, and any precursors. For example, the scale and focus of activities and processes relating to individual land tenure and heraldic entitlements at non-peerage levels - the Visitations were not yet underway, so what was their forerunner; and did they conduct any kind of survey for revenue and fealty purposes; and do we know to what extent Welsh speakers gained high office to assist with overcoming language barriers?
So there's actually a perfect study which analyses this topic in a comparative context, with the French crowns imposition of power after the Albigensian Crusade, it's by James B. Given State and Society: Gwynedd and Languedoc Under Foreign Rule (1984?) there are some methodological issues but the basic analysis is correct - essentially that the Conquest wiped out the top tier of nobility but left in place the administrative group; the imposition of a castle-based infrastructure allowed easier picking and choosing of allies in Wales but the fourteenth-century was stable because the basic society was unchanged and there was an easy way of supporting crown faithful through patronage for castellan roles
To branch off that: How many people in Wales would have spoken English in 1282 ? Also did the relatives of Llywelyn ever try and reclaim Welsh land at some point or another? Thanks