See the README.md file located in $deploy/sas-bases/examples/scaling/ha. There is a transformer in $deploy/sas-bases/overlays/scaling/ha/enable-ha-transformer.yaml you can add to your kustomization.yaml file that will convert your stateless services to HA. The stateful services are already HA by default (apart from CAS).
Once making the change to kustomization.yaml you would need to rebuild and apply your site.yaml.
The compute and launcher services are stateless services so would be captured by the previous patch. The compute/connect/batch servers launched are launched on demand. Having multiple compute nodes in your node pool would prevent an outage from one of those nodes going down.
-- Greg Wootton | Principal Systems Technical Support Engineer