Well, that part about the Northern Black Sea Coast is not exactly true. Yes, Varna is overpopulated by tourist in the summer, but Shabla, Kamen bryag and Yailata are not. Dulboka is definitely worth going to: it's a mussel farm and it has a large menu of seafood specialties. Besides, the Southern Coast is overpopulated in summer, too... just take a look at Kiten or Primorsko. The Northern Coast, especially the part that's closer to the Romanian border is wilder and rockier, which makes it even more beautiful in my opinion. But hey, what do I know, I come from Varna and it's understanable if I'm partial :)