I have Heaven, Valley, Superposition, WoT enCore, Forza Horizon 4 and Neon Noir. I'm going to test them on the 5700XT at stock settings then install the 6800 and test again, then again at a memory underclock (if I can work out how).
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Couldn't find a way to reduce the memory clock - however I could increase it to 2,138MHz (stock is 2,000MHz).
Results:
Neon Noir; 4K, RT Ultra: stock: 3,769; +138MHz: 3,808
WoT enCore: 4K, Ultra: stock: 16,933; +138MHz: 17,052
Superposition: 4K Optimised: stock: 11,611; +138MHz: 11,680
Forza Horizon 4: 4K Ultra Adaptive: stock: 125 FPS; +138MHz: 126FPS
Heaven and Valley would not let me set the resolution to 4K so ran them at 2560x1440:
Heaven; 2560x1440; AAx8 Ambient Occlusion, Volumetric Shadows, Refraction: stock: 3,154; +138MHz: 3,170
Valley: 2560x1440, AAx8, Ambient Occlusion, Volumetric Shadows, Motion Blur: stock: 5,154; +138MHz: 5,216