How did the proximity to Slavic and nomadic tribes influence Byzantium and the empire of Charlemagne?

How did the proximity to Slavic and nomadic tribes influence Byzantium and the empire of Charlemagne? What could have changed in relations between Byzantium and its neighbors by the baptism of barbarian tribes?

Very often, between the Slavic tribes and Byzantium, as well as the empire of Charles, there were clashes on the borders. Naturally, this forced the rulers of these states to take certain measures, but neither the Franks nor the Greeks dared to conduct major military campaigns against the Slavs. But those, in turn, often made raids. Especially if you take Byzantium, whose rich cities were often the target of attacks.