Child actor component is a component “containing” actor, or rether operating actor so it acts like component, by moving it to component world position on every tick and handle its life cycle (spawning and destroying) to keep in sync with parent actor. Child Actor Component is a component, and component is not actor and vice versa, so you cant cast it. What you getting is child actor component class so you should cast to that
From there you can use GetChildActor() to get actor from component