Running on Windows 11 with a 6900XT and Vulkan and DX11 look effectively identical as far as I can tell but Vulkan runs a lot faster and doesn't stutter when loading a new area.
Unfortunately though it tends to crash on tab out which means I need to use DX11 because I play with friends.
Yes. It's not really meant as a visual improvement but as an efficiency improvement. Sadly it does seem (for some, myself included) that the Vulkan build needs a bit of work. For me it crashes all the time, and Larian themselves mentioned that it isn't quite as stable as the DX11 build.