Bootcamp BIOS mode with sound or EFI mode with eGPU?

[yashiharu]

I spent hours and hours to disassemble the iMac 2011 and install windows with different modes repeatedly.

So the truth after all:

Either:
a) BIOS mode Bootcamp Windows 10 with sound, but no eGPU.
or
b) EFI mode Bootcamp Windows 10 with eGPU, but no sound. (Internal speak won't work, even with USB audio device)

right?

 

[Nexeption]

The efi problem of sound is related to the DSDT, here is a fix :
https://superuser.com/a/1401672/1002220