Difference between returning Task VS returning awaited Task from controller method

Question

I have a ASP.NET WEB API controller with a method like this:

[HttpGet]
[Route("some/route/to/endpoint")]
public Task<Data> DoStuffAsync()
{
    var somevar = Guid.NewGuid();
    return DoSomeInternalStuffAsync();
}

private async Task<Data> DoSomeInternalStuffAsync()
{
    var result = await SomeReallyInternalThingsAsync();
    return result.Data;
}

What is the difference on eliding the async/await and to actually use it like:

[HttpGet]
[Route("some/route/to/endpoint")]
public async Task<Data> DoStuffAsync()
{
    var somevar = Guid.NewGuid();
    return await DoSomeInternalStuffAsync();
}

I read a lot of articles and Stackoverflow posts, but it is still unclear to me:

1. What is the internal handling of a controller method returning a Task VS returning an awaited task?
2. Will the controller method be awaited in each case or is returning a Task on a controller method a pure synchronous operation?

Articles read so far: Eliding async await, Asynchronous Programming, Stackoverflow Thread 1, Stackoverflow Thread 2

Update: My questions are answered in the comments.