Pretty much exactly what it says in title-by how much should I upscale my piece? Is there no specific requirment or should it be exactly, say, 2x or 5x or something else?

I think the upscaled is just for the webpage so you can choose whichever you prefer (I went with a 4x) for the download keep it 1x.

At least this is my understanding from reading various community posts.

I went 1000% for the screenshot image. The download png has to be 1x scale.