To check ovelapping:
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you can just check every now and then if the actorenemy and the actor spawner overlap with this
Is Overlapping Actor | Unreal Engine Documentation -
you can also use the standard event for ovelapping , you have to define your collision to generate the overlap and then you can use this nodes to check What actor is leaving and entering the are.
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you can use also raycast to , Randomly cast a ray to the ground in search for a position for spawn.
You can generate some random values in the range of your “area”
Using a Single Line Trace (Raycast) by Channel | Unreal Engine Documentation