Hackintosh without iGPU

Hi, I’ve been trying to get macOS working with my current setup:

ASUS H87 Pro Intel Xeon E3-1230v3 (no iGPU) Radeon R9 390

I was able to install and use it by plugging into the 390. I wasn’t able to get the GPU working properly though. Everyone was always suggesting to set the iGPU as primary GPU which obviously is not possible in my setup.

Therefore I’m thinking about buying a new GPU which works without iGPU. So far I’ve read that all the AMD Polaris GPUs will not work.

Using a NVIDIA Pascal GPU seems to work though. Is that correct? Is dual-booting Windows still possible then? Will I be able to use the actual GPU for macOS and Windows?

Thank you!