In terms of Balkan OC it's basically Albanian OC and Serbian/Montenegrin OC that have the most widespread reach. The others can't compare.
I assume the "Bulgarian mafia" has some power in Bulgaria itself, but international activities are very limited. Most Bulgaria-connected criminal cases I come across here in Belgium involve Turks from Bulgaria instead of ethnic Bulgarians and it most concerns illegal contracting and prostitution; more often than not connected to established Turkish criminal organizations.

Montenegrin OC elsewhere a lot of times is just looped under the "Serbian mafia" umbrella. To be fair, a lot of it seems to involve Serbs from Montenegro and "ethnic Montenegrins" themselves are in essence basically ethnic Serbs but describe themselves as "Montenegrin" in order to identify with the more mountainous folkloric background of that region.