This new driver (along with the modules Nvidia have released as OSS [1]) are kernel drivers and do not break userspace. NVK is a Vulkan implementation for Nvidia GPUs as part of the Mesa project (the same project that AMD's userspace drivers are a part of, even though AMDs kernel drivers are in tree). They are both needed to make a cohesive driver.

[1] https://github.com/NVIDIA/open-gpu-kernel-modules