I just ran a benchmark for Vulkan after I changed it in settings. First this is my PC:
Windows 10 Pro
Intel i7-7700k @4.5 with turbo enabled (no overclock)
16gb PC3200 DDR4 Ram
Geforce 1070 8gb
Asus Strix Soar Sound Card
750 watt EVGA PSU
Latest Nvidia drivers
I play Fullscreen 1440p with a Gsync Monitor
1440p, Fullscreen, DX12, No Vsync, No multiple GPU and No 3rd Party Overlay checked
MSAA: 2X, PLQ: High, Glare: Mid, TerrainOQ: Ultra, Shading: High, TerrainShading: High, Shadow: Low, Texture: High, Environmental fx and clouds: Enabled
With those settings I get an avg overall framerate of 82 - CPU is 103
When I enabled Vulkan (which was the only thing I changed) my FPS avg dropped to 42 and CPU was still 102.
Really strange dip for my system with Vulkan. I know with Doom and Vulkan my avg FPS on ultra quality is over 100... granted I understand two completely different games. Just an example.
For now I am going to just use DX12.
Thanks and hope this helps!