Broadly speaking, Ignite assumes all your nodes are close to one another. You could make it aware of multiple zones by using custom affinity functions, but it's not straight-forward. There are also third-party solutions (I work for GridGain who provide one) that support data centre replication, etc. that would work in this situation
Yes. I would suggest that thick clients should be part of your Kubernetes infrastructure (since they become part of the Ignite cluster topology), but you can connect a thin client just by opening the right ports. You can use Kubernetes load balancing / round robin to connect to any node