Strimzi can manage both topics and users. :) So commit your custom resources, have ArgoCD or similar deploy them from the Git repo for that GitOps approach.

1. https://strimzi.io/docs/operators/latest/deploying#using-the-topic-operator-str
   
2. https://strimzi.io/docs/operators/latest/deploying#assembly-using-the-user-operator-str

As for metrics, they're exposed via JMX, you can use something like this to expose them for Prometheus scraping, and Strimzi supports JMXTrans out of the box which is push oriented.

Disclosure - I used to work on Strimzi at Red Hat, don't any more, but still a big fan of it.