Kassian Wren's walkthrough explores the integration of Gatsby with TypeScript and the use of generated GraphQL types to enhance application development. The guide emphasizes the compatibility between Gatsby's GraphQL data layer and TypeScript's type-checking capabilities, which collectively reduce runtime issues and streamline development. The process involves setting up a Gatsby project, configuring it to auto-generate types for GraphQL queries, and connecting to the GitHub GraphQL API to retrieve data about the most-starred repositories under the gatsbyjs account. By using GraphQLClient and the gatsby-node.ts file, developers can source data into Gatsby's data layer and query it on the index page, with TypeScript ensuring type safety throughout. The tutorial illustrates how TypeScript not only benefits GraphQL queries but also enhances the overall development experience by providing type safety, auto-suggestions, and improved workflow efficiency.