All transformed image should look pixel perfect in 100% zoomed in even in @1x settings. However, when you're looking to export images with @2x or above resolution, the source would have provide 4 times as much pixels. Enhanced Image Quality is here to solve the issue. @1x and @2x depends on the source of the artboard size, so the higher the source is, the clearer the rendered image. It's fast and works well with general UI perpective transform.
Max resolution depends on the shape, it looks into the target's shape size and find out the best resolution it can be rendered to make exporting in @3x as clear as possible. Works best for rendering small vector UI components into larger canvas.
*Free version will see a watermark in @2x and Max image quality setting.