Cannot find some features on my UEFI BIOS Utility

Hello, I need to disable my integrated graphics card and set the GPU to PEG/PCIe, and this is supposed to be in a section called Chipset configuration somewhere in the advanced settings, but such section is nowhere to be seen. I do, however, find an Onboard Devices Configuration section, but all it allows me to do is enable the Audio and LAN Controllers

There's also a section in Advanced\ System Agent Configuration \ Graphics Configuration > But all I'm allowed to move is the Primary Display (i GPU, PCIE or Auto), the i GPU Memory (Auto or 32-1024M), Render Standby and iGPU Multi-Monitor I use an asus H81M-E mobo

To be more specific, what I'm trying to do is a hybrid dual monitor setup on my Hackintosh High Sierra build, making use of both the onboard and my AMD Radeon R7 250 graphics card, by Asus

However, I'm in the middle of getting such graphics card to work with High Sierra (which is why I need to find the bios chipset settings) and then I'd have to figure if it's possible to work with both GPUs.

Thank you for your time, have a good one