I've been everyplace you mention but Tirana and Skopje. Tirana is in the plan for September; but I will be getting there by car from Podgorica so cant help much.
I enjoy Kiev a lot. Enough for return trips; but its the history making in progress and the kindness of the people that account for about half of my interest. If you are a church and tower guy then its good for 2 full days. If you have more time run down to Odessa for a Thrus, Friday or Saturday evening. Pretty amazing.....
Brasov didn't light my fire like it does for many.
I enjoy Sofia a lot; but there is so much in Bulgaria that is amazing that its hard to spend much time in Sofia.
Bucharest is one of those places you will be glad you spent a full day in. The experience will stick with you a long time. But after that full day you may be wondering how the hell do I get out of here.