PUBG, Arma 3, etc are poorly optimized games. You will have issues with those games regardless of the GPU you use. PUBG is still in early access and given its success, I think that it be optimized better moving forward. I have twin 1080ti's in sli and still get frame drops in PUBG. Dont even get me started on Ark Survival Evolved.
But this is the best time in the world to own a 1060 6gb. With the whole mining craze going on right now I would throw that on craigslist to pay for an upgraded GPU. Im not sure what they are going for, but I know that 570/580 are around $400/500 each. You may be able to get the same for a 1060 6gb and upgrade to a 1080 for next to nothing.
If you play those games with a 1080 on a monitor with gsync, you will never notice the FPS drops as gsync matches the refresh rate on your monitor to the refresh rate of your GPU.