The Hasura GraphQL engine automatically generates your GraphQL schema and resolvers based on your tables/views in BigQuery. You don't need to write a GraphQL schema or resolvers. See How Hasura GraphQL engine works for more details.
The Hasura console gives you UI tools that speed up your data-modelling process, or working with your existing database.
The Hasura GraphQL engine lets you do anything you would usually do with BigQuery by giving you GraphQL over native BigQuery constructs.