It is always best practice to keep the /conf in code i.e.using any source code management (git) and it will be deployed as part of the deployment package.
In AEM as CS, the ui.content package contains all content and configuration. The Content Package, contains all the node definitions not in the ui.apps or ui.config packages, or in other words, anything not in /apps or /oak:index.
Required, complex content structures (ie. Content build-out that is builds on and extends past Baseline content structures defined in Repo Init.)
Governed tagging taxonomies
Legacy etc nodes (Ideally, migrate these to non-/etc locations)