It's YouTube. This is the place where you'll see a guy appear to pull an orange out of a book, or pour milk into a TV screen. That's the magic of video editing, you can't always trust what your eyes can see.
That being said, 20 FPS is very low for that system.
https://www.techspot.com/review/712-arma-3-benchmarks/page5.html
It may not be well-optimized, but when Techspot tested with the 700 series-based Titan (roughly comparable to your GTX 970, http://www.tomshardware.com/reviews/gpu-hierarchy,4388.html), they had no trouble getting more than twice your FPS with even 1st-gen Core i7 CPUs & AMD FX-series CPUs -- & most of the Core i5/i7 & FX CPUs were well within a few FPS of each other.
Have you checked your CPU & GPU temps...