Yeh, right now most Dx12 games are ports from Xbox, not ground up dx12/vulkan for PC.Yup, I even can't run the free DX12 games (Forza Motorshort 6: Apex(Beta)), it just hang on the loading screen...
I think both those low level API will help low to mid range CPU even more, you can see it now with dx12, but you don't see it mentioned much as the combo is low end CPU with high end GPU, were this shows the most.It should help every game, unless the dev using it incorrectly, or the bottleneck is on the GPU.
Not a realistic user system really.
It is talking about low range CPU because most laptop has dual-core i3 and i5, for example, I am playing Planetside 2(DX9), and it is getting 90% cpu usage because of dual-core.
By reducing overhead for DX12, then it should improve the performance a lot higher than 4 core CPU, unless the game can using 90% of 4 core CPU too, or the bottleneck is the game are just waiting respond from DX api without doing anything(means it block the main thread and any other threads).
They also supported you to use AMD and Nvidia graphic card together by rendering half of the screen, but it is a bit bad as it depend on the complex of the half of the screen that you assign to the graphic card.
So if you assign complex part of rendering to weak graphic card, but simple part of rendering to strong graphic card, then it will just getting blocked by the weak graphic.
Then, it will depend on the optimization of the dev to fix(workaround) this issues, or the multi-gpu rendering is still a issues even you has used DX12.
PS: Someone that having a lot of knowledge and better than me said something about this.