Is it possible to communicate with both Prisma and Prisma-Client Application APIs at the same endpoint, or from the client do I need to make calls to different endpoints depending on the data I need?

Yes that is possible, but it's not a common use case I'm aware of.

So it's more common to either a) communicate with either API independently on the front end, based on the needs of the request or b) replicate all the needed CRUD operations from Prisma in the Application?