Based on a video comparison by FlightlessMango you'll observe that in a comparison between Linux and Windows versions, Red Dead Redemption 2 runs faster on Linux with an AMD graphics card.

The man made use of a Core i7 8700k with 16GB of RAM running at 3200Mhz and an AMD Radeon Vega 56 graphics card for both operating systems. For Linux, it used the drivers Mesa-git 20.2.0 , amdvlk-2020.Q2.4-1, and amdgpu-pro-20.10 . For Windows, meanwhile, he used the AMD Radeon Adrenalin 20.5.1 driver.

You'll notice that the game performed a notch better on that Linux platform than on Windows 10. Now we shouldn't make it too dramatic, as at 1080p, the benchmark on Linux was faster by 3-5FPS in average frames per second. For NVIDIA that is the opposite, and seems to run slower.

Red Dead Redemption 2 actually performs better on Linux than Windows with AMD Graphics