I've just always followed the Arch wiki, and never tried using Vulkan without vulkan-radeon on my one PC with an AMD card. The wiki states: "Install the mesa package, which provides both the DRI driver for 3D acceleration and VA-API/VDPAU drivers for accelerated video decoding." and "For Vulkan support install vulkan-radeon (lib32-vulkan-radeon for 32-bit applications).".The vulkan page itself says:

To run a Vulkan application, you will need to install the vulkan-icd-loader package (and lib32-vulkan-icd-loader from the multilib repository if you also want to run 32-bit applications), as well as Vulkan drivers for your graphics card(s). There are several packages providing a vulkan-driver and lib32-vulkan-driver:

    AMD: vulkan-radeon (or lib32-vulkan-radeon)
    Intel: vulkan-intel (or lib32-vulkan-intel)
    NVIDIA: there are two implementations:
        nvidia-utils (or lib32-nvidia-utils) - NVIDIA proprietary
        vulkan-nouveau (or lib32-vulkan-nouveau) - NVK (part of Mesa project)

The vulkan-radeon package provides the ICD (

# pacman -Qlq vulkan-radeon | grep -v '/$'
/usr/lib/libvulkan_radeon.so
/usr/share/drirc.d/00-radv-defaults.conf
/usr/share/licenses/vulkan-radeon/license.rst
/usr/share/vulkan/icd.d/radeon_icd.json

); so does nvidia-utils (

# pacman -Qlq nvidia-utils | grep -i icd | grep -v '/$'
/usr/share/vulkan/icd.d/nvidia_icd.json
/usr/share/vulkansc/icd.d/nvidia_icd_vksc.json
)

, but mesa does not.