Data mining: Clique based clustering to make comparison in social network analysis
There are over 300 social networks captured in the Index of Complex Networks.  Thats usually the best place to start.
While your quantitative method is not very clear, it sounds like you could start with networkx and use something like find_cliques.  There is also a community detection method built for all types of subgraphs, not just cliques Benson et al. (2018).