ActorUtil & ActorProxy

Should I be using these 2 actors at all, or are they just for easy actor creating/rendering in the game code?

ActorUtil isn't even an actor, it's a namespace with a bunch of actor-related functions. Every single actor you create in Lua involves at least one indirect ActorUtil call.

ActorProxy is useful if you want multiple actors that have the same base image. If it seems useful to you, use it.

What do you mean by "same base image"?

ActorProxy just has the game draw the target actor again with the ActorProxy's parameters.