QQ: Is there a declarative way to set the configuration (feature flag state, user management, environments etc)? Something like a yaml file and / or a terraform provider? Or everything is done through the console and if something happens we restore the entire state from the DB?

Feature flags and users are all stored in the database. We do have a yaml config file you can use if you are self hosting, but it's only for data sources, metrics, and organization settings right now. https://docs.growthbook.io/self-host/config

thank you jeremy!