Hmm, Vulkan seems a bit.. hitchy on my 970, switching to OpenGL seems to help.
You're not the first person to experience this, I also have a 970 and have it, so OpenGL is advisable to use. I've seen quite a few with this problem. I was only seeing a max of about 7-10fps improvement with Vulkan and while thats not to be sniffed at, I'm still way over 60fps at 1080p so it's not like it makes much difference.