Platform level Config and separate Device/Entity Config

I was looking at the Calendarific custom integration trying to envision a way to make everything configurable via config_flow.

Currently, it requires the platform-level config to be set in the configuration.yaml. Then, the individual holidays can be added via config_flow or yaml. Each holiday has separate configuration options for specific icons, number of days before the holiday to change the icon, etc.

Is there any other similar integrations that I could use an example for how to do all of this with config_flow?