Hello
BF1 with dx12 is an Nvidia killer, but not in that sense. Right now Nvidia gets nothing out of dx12.
When the dx12 came out on Civ VI my rx480 started pulling +18FPS, note that on dx11 i was already having the same fps as a gtx 1060. And on BF1 i got +16FPS when switching to dx12.
The thing is dx12 uses all the features of the graphic card meaning, dx12 uses the async compute to normalize and improve usage of the resources, right now cude core cant do anything to async compute, the software solution that nvidia gave is crap.
So my advise if make sure you have dx11 running on all those games that already support dx12.
Maybe the next gen 11XX will have support for dx12, until then keep using dx11.