Okay- as I tend to advise most mods on the Balkans due to Rhomano-phile tendencies!
First and foremost, the frontier of the Bulgaria province should lie along the river Danube, and not intrude into Wallachia. The Danube was always the frontier of the area, under both Rhomanians (Byzantines) and Ottomans.
Durazzo should be renamed to its Greek title "Dyrrachion"- the Latinised version of this is "Dyrrachium". It certainly shouldn't be the Italian "Durazzo", anyway.
Athens was really not a very important city in the medieval era, though Corinth was. If you want another Greek city to replace Athens, I'd suggest Larisa- otherwise, just take it out, and get a new slot to "spend" on the Middle East somewhere. Western Anatolia would be my suggestion...
Scopia should be replaced by Ochrid, the capital of the first Bulgarian Empire and a major city in the region.
Sofia should get its Greek name of "Sardica".
And here are two possible ones- swapping Arta for Nikopolis (both were important, Nikopolis more so in the 11th and 12th centuries, Arta afterward) and Adrianople for Philippopolis (again, for the early campaign, Philippopolis was more significant, for the late one, Adrianople was).
Constantinople should certainly be a huge city, and Thessalonica should be a large one- it's a little known fact, but Thessalonica was likely the second largest city in early medieval Europe, larger even than Milan or Paris.