The DX11 renderer won’t bring anything closer to UE4 by default. you have to manually use the DX11 features to see any graphical change of any kind. in short:
- Bokeh Depth of Field - manually enable in your postprocess chain to get bokeh
- Tessellation - use it in your materials
- Image Based Reflections - use it in your scenes
- Deferred Shading - used automatically, does not provide eyecandy benefits of any kind (theoretically just better performance)
- Full Scene Anti Aliasing (MSAA) - no clue why it’s featured as DX11, UE3’s DX9 also has it
- Screen Space Subsurface Scattering - use it in your materials
using all of the above features will however still not bring you closer to UE4 in any significant way. you don’t get PBR or probe-based image-based reflections or some of the other staple UE4 features like image-based lensflares 
the unexplained noise / white speckles are some of the issues I remembered that were unsolved. I suspect it might be caused by bad handling of not properly normalized normal input in the material, which if it’s the case they could potentially be fixed in the material itself