I'm not a very experienced GM, and I'm looking for advice on what the "best" approach is to selecting creatures/monsters for combat encounters. I'm not really thinking of how to set up encounters of the proper level or difficulty since those rules are pretty straight forward, and there are some really good tools online to help in that process.
I'm more interested in how you "mix and match" creatures into an encounter (or maybe more encounters in a bigger dungeon) in a way that feels like it makes sense in the Golarion/Lost Omens setting? How do I know which creatures would work together thematically?