You can customize the compute resources on a job basis in ECS:
https://docs.dagster.io/deployment/guides/aws#customizing-cpu-memory-and-ephemeral-storage-in-ecs
As far as the choice between K8s/ECS is concerned, I don’t feel comfortable giving advice. ECS is much simpler and easier to pick up than K8s, and it might get you 90% of the way there. Whether or not that’s enough is gonna be up to you and your team to decide.
(also I’m not a k8s pro so there’s probably other people better equipped to answer that)