If you use QEMU plus KVM (Kernel Virtual Machine), you can say goodbye to dual boot as the virtual machine is run with near native performance. For playing windows-only games, the solution is GPU passthrough, which allows allocating a GPU for the virtual machine providing the maximum gaming performance.
Does that work on all hardware? I've got laptops, and could maybe use hybrid graphics. I'll look into it, thanks!
Edit: so this doesn't work for muxless laptops (I've looked into it before and forgot). The discrete card runs through the Intel iGPU regardless if hybrid graphics is enabled or disabled.
The vBIOS can't be accessed directly, so it will result in an error. Some people got this working anyway, but it seems that it's unstable and/or results in low performance.