1 month in the Balkans in summer

Looking to spend a month from mid July to mid August in one of the following destinations where I have cheap flights, do you have any advice on which one to choose?

Requirements: - not too hot - high speed internet and co-working space (needs to do some focused work) - can easily meet other Digital nomads - possibly a good dating scene

• Bulgaria: 1-2 weeks in Sofia, then Bansko. My only concern is that Bansko may be dead in this period if the year.

• Romania: Bucharest and Brasov

• Polonia (Krakow). Technically this is not Balkans, but I'd like to include it.

What is your experience and recommendations?