What are the various Classes and Methods of finding objects in the World? (C++/BP)

Besides GetAllActorsOfClass, what are other methods for finding specific Actors in the game?

Also…in C++, how exactly do you call these functions? They use parameters such as:

static void GetAllActorsOfClass
UObject * WorldContextObject,
TSubclassOf < AActor > ActorClass,
TArray < AActor * > & OutActors

I’m not sure what to pass for WorldContextObject.
TSubclassOf < AActor > ActorClass…i would just pass the class name here?
TArray <AActor *> & OutActors is a pointer to the Array of Actors that this class will populate?

I suppose I could use volumes on the Agents that are using my Behavior Tree…

I’d really like a different solution for this…such as FindNearestActorInRadius or something…would find all Actors in Radius, check what Class they are, and then check distance on the appropriate classes and return a pointer to the closest