Is the Canon RF 100-500mm F4.5-7.1 L IS USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 500mm f/7.1 test image. Observe the contrast and resolution of these results.
Is the Canon RF 100-500mm F4.5-7.1 L IS USM Lens set to 500mm f/7.1 sharper than the Canon EF 200-400mm f/4L IS USM Extender 1.4x Lens set to 800mm f/8.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.