What is the practical difference between a property and a knowledge graph?

Context:
My use case appears to be different that that of most people. I am a social science researcher studying social organizations, systems etc..... The reason I am not using a normal sociogram or social network graph is because there the edges are too simple. They do not carry sufficient meaning for the complex relationships that I am trying to understand between my entities. Which is what brought me to knowledge graphs, where both the edges and the nodes carry meaningful information, or at least so i've understood it so far. From what I understand the ontology describes how everything connects together in practice at the general schema level ie entities and relationships. But if I am understanding correctly and idk if I am, property graphs don't have ontologies, but rather just labels?

Does anyone have any suggestions?