I'm running an R9 290 and a Benq XL2420T, And since i updated my video drivers i'm getting Tearing on YouTube video, and am now also getting artifacts in CSGO on anything higher than 4x AA, No OC.
Please try updating to Crimson 17.9.3 and let me know if you are still having issues.
Have you tried disabling hardware acceleration in your browser? YouTube issue.
Wattman AA setting > Anti-Aliasing - Is there a difference between Enhance Application Settings and Use Application Settings
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