Is the Tamron 150-600mm f/5-6.3 Di VC USD G2 Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 840mm f/11.0 test image. Observe the contrast and resolution of these results.
Is the Tamron 150-600mm f/5-6.3 Di VC USD G2 Lens set to 840mm f/11.0 sharper than the Tamron 150-600mm f/5-6.3 Di VC USD G2 Lens set to 400mm f/8.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.