This is all very well possible within DNN given the requirements, the solution(s) however are going to very greatly depending on the skillset you are working with and/or the technical aptitude that you may want to bring to the table, as well as some possible considerations regarding how much load you really want to handle.

I know this is a bit of a non-answer, answer, but there are a lot of things that you could consider/do.

* If you aren't a developer type - You could utilize various third-party modules for file management, signup etc.  including some of the form builder or other low-code solutions to piece it together.

* If you are a developer type and want more control, you may treat DNN as more of a framework and then implement  your solution on top of, but controlling things such as CDN storage, payment, and API generation on  your own to set a standard and consistency.

Some may suggest other solutions (Native .NET Core, etc), but it really depends on your task at hand.

With a audio/file streaming service, I would have some considerations/concerns about servicing the actual files through .NET in general if very high throughput as IIS isn't the greatest at static file sharing.

I've built systems with many of these components, in a few ways, with DNN, without DNN, and otherwise.  Feel free to reach out directly if you want and I can at least share a bit of my experience.