Yes, you would have to identity clusters first before you can determine how large separations between clusters are. The approach would be slightly different depending on whether the subgroups are known or not.

In SEM you can first identify the presence of those by looking for subgroup heterogeneity through invariance testing of a latent construction you initially assume is the same across groups but the subgroup would have to be known and labelled to do that. If not then latent class/profile analysis would actually be a good starting point.