Feature flag can (usually does??) have another meaning, as a technical feature rollout mechanism, so you can roll back quickly without a deployment. A way to manage risk on teams that make hundreds of commits/deploys a week. You can then often send a certain % of traffic through the feature or not to look for early warnings.

I don't like feature flags for config. Just build a config system into the product UI - a settings page basically! That might have some bits you configure as the site owner, and some that are self-service.