Is the Sony FE 200-600mm F5.6-6.3 G OSS Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 200mm f/8.0 test image. Observe the contrast and resolution of these results.
Is the Sony FE 200-600mm F5.6-6.3 G OSS Lens set to 200mm f/8.0 sharper than the Sigma 150-600mm f/5-6.3 DG OS HSM C Lens set to 200mm f/5.6? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.