The AWX-Operator only controls how many web/task replicas there are (task replicas are also known as control nodes and are members of the controlplane Instance Group in AWX). It doesn’t support HPA yet, but there’s been some discussions about how to implement it and test such a feature.
Job slicing on the other hand has nothing to do with the operator. When you queue up a job with multiple slices, AWX’s control/execution nodes spawn the automation-job pods (not the operator!) up to the maximum concurrent job count defined for all available Instance Groups (default is unlimited!).
I went over how you can tune that here.
I don’t know anything about EKS or karpentor, but if the k8s cluster can scale up to handle a high number of automation pods, then I don’t see any reason why you couldn’t take advantage of that. You would just need to make sure AWX’s Instance Groups only spawn a maximum count that coincides with whatever maximum you allow the k8s cluster to scale to.