we are attempting to move to ARC (actions runner controller) which means running our actions in Kubernetes pods instead of EC2 instances/ASGs. Basic stack taking 5 min to preview

Upping the SSD types makes a big difference but I'm not sure you can do that with the hosted agents. The packer for the hosted agents is available here https://github.com/actions/runner-images We build images from that and have scale set agents (https://learn.microsoft.com/en-us/azure/devops/pipelines/agents/scale-set-agents?view=azure-devops) with fast ssd running during work hours and fall back to hosted agents for off hours. This is for Azure DevOps which doesn't help but the same might be able to be done with self hosted runners.