Is the Sony FE 100-400mm F4.5-5.6 GM OSS Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured mm f/ test image. Observe the contrast and resolution of these results.
Is the Sony FE 100-400mm F4.5-5.6 GM OSS Lens set to mm f/ sharper than the Sony FE 200-600mm F5.6-6.3 G OSS Lens set to 400mm f/11.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.