I fully understand that most what is written about king Arthur is shrouded in myth, many stories having been written several centuries after his time period.
Most material I found focuses on the stores themselves, or mentions the geopolitical landscape but without containing enough information to build a realistic image of a domain a 6th century king or warlord or whoever the Arthurian legends were originally based on, could have had in that area.
What I'm interested in, is how much area he could probably have controlled, the number of towns, villages, castles, and a rough estimate of the population. If written material is scarce from that time period, and what we have usually doesn't focus on these kinds of information, what can we infer from what we know about typical kingdoms, lifestyle, economy, etc. of that time period?