the volume node affinity thing is a little annoying, afaik there's no way to specify which zone your nodes are placed in, so any PV created in one zone, might not be reusable if the nodes shuffle around and you're left with no nodes in the same zone as the PV

Yeah, you need to make sure every AZ has instances, so if you use the HPA you need an ASG per AZ, or use Karpenter.