Nvidia drivers don't tend to be as performant under linux.
With AMD instead of using the AMD VLK driver, you would use the RADV (developed largely by valve). Which petforms better.
Every AMD card under linux supports OpenCL (the driver is more based on graphics card architecture) and you install it very easily. Googling it with windows found pages of errors and missing support.
Blender supports OpenCL. I bet the 2x improvement is Blender being able to ofload rendering to the AMD graphics card.
Also this represents the biggest headache in Linux, lots of gamers insist they can only use Nvidia cards. Nvidia treats linux as an afterthought as best or deliberately sabotages things at worse.
AMD embraced open source and so Linux land is much nicer on AMD (and to a less extent Intel).
The results here will probably be a DxVK quirk, lots of "Nvidia optimised" games have game engines doing weird things and the Nvidia driver compensates. DxVK has been identifying that to produce "good" vulkan calls.