Now the only way to get a config is to use atPath method, which requires ConfigClass creation.

That looks like an overhead for simple cases when Config is minimalistic
https://github.com/elastic/kibana/blob/75d01eed4007e7f3675b68c5b87edd1662dcd9d9/src/core/server/plugins/plugins_config.ts
We can add an alternative method that returns validated config and end users can map it to a ConfigClass if needed.