VMWare Workstation? Even on Linux it supports up to DirectX 10 only. You won’t be getting full GPU DirectX 11 support in a virtual machine like that to use the GTX 970 properly with UE4.
If you want to use UE4 you need to boot Windows10 natively and let it use the whole 32GB RAM because it will need those. UE4 is fast if it can access the GTX 970 directly and 32GB RAM.
It is pretty obvious that it is slow in a virtual machine with just 8GB RAM and emulated DirectX 10 support with no direct access to DX11 on the GPU.