Impossibility to configure child agent nodes differently (for A/B testing, progressive alert rollout, etc)

We’re trying to configure parent.configs with different user configuration files for a subset of nodes, to achieve partial rollout of a change in alarm notification settings; we have a big cluster and don’t want to switch on this change in all nodes at once.

Is that possible with chart config options?
Can we patch config for certain nodes if not possible with helm chart?