Hey there! I'm happy to help!
One thing that the Balkan Mountains have done is create very distinct cultures. Every location has different cultures, but these mountains are very large physical barriers to cultural interaction, so this has led to a plethora of different ethnic and cultural groups in the Balkan region.
Another thing that they have done is create a sort of hierarchy where those that are more well off live in the valley, further away and from the mountains, and those who may not be as well off, considered inferior, or simply desire to practice transhumance, herding, or being a nomad will be dwelling in the mountains. It creates different "zones" based on the geography of the area.
A final thing these mountains have done is create cultural tension in the Balkan Peninsula. Since so many of these groups develop isolated from from other cultures, efforts to unite these groups usually fail and it leads to rancor between these distinct groups. This is why this area has been very war-torn before in states such as Bosnia and Herzegovina.
Have a wonderful day and keep on learning! :D