Vercel provides the ability to route requests based on the three different configuration properties:
While these properties provide different methods and degrees of flexibility when it comes to routing, it is not possible to route based on letter casing with configuration properties.
By using Serverless Functions, you can take advantage of code to achieve whatever outcome you require.
For more information on how to do this, take a look at the Dynamic Routing support article which contains code examples that allow you full flexibility over routing, the ability to handle errors, and caching headers for maximum performance.