I have seen several posts on this topic but the answers are complicated. Suppose I have the following code:

static async Task Main(string[] args)
{
    await Task.Run(LongRunningTask1);  

    await LongRunningTask2();

    await Task.Run(LongRunningTask2);

    Console.ReadLine();
}

static void LongRunningTask1()
{
    Thread.Sleep(2000);
}

static async Task LongRunningTask2()
{
    Thread.Sleep(2000);
}

Console.ReadLine();

Each of the above await expressions does the same thing.
Can someone give me a simplified summary of when you would use each one?

Also, which of the three await expressions create a separate thread? I assume that it is the first and third. If the second uses only the UI thread, then how is the execution time apportioned between Main() and the awaited task?

I have read that the second choice slows down the GUI (if, for example, Main() were instead a button click handler for a WinForms program). Then why use the second choice? What does it buy me?