Found this tech article explaining about the Mux Switch on a laptop and how it works plus how BIOS is involved the Mux Switch capabilities: https://www.howtogeek.com/780933/what-is-a-mux-switch-in-a-gaming-laptop/
The MUX switch lets consumers enable or disable the iGPU, thus allowing them to route all graphics rendering directly from the dGPU to the laptop display when needed. Although this severely impacts the laptop's battery life, it provides a significant performance increase and lowers latency in games.
The multiplexer switch is a microchip on the laptop's motherboard, which physically changes the connection between dGPU and the display, and it's accompanied by software that allows consumers to communicate with the chip. Unfortunately, as it needs specific hardware to be present in a laptop, you can't simply upgrade your laptop to have a MUX switch.
Related: When Are Integrated Graphics Good Enough on a PC?
Moreover, a reboot is required every time you toggle the MUX switch to enable or disable the discrete GPU mode. But it is a small sacrifice to get the reduced latency and increased frame rates. Asus says bypassing the iGPU can result in an average of 9% gain in frame rates. Some games like Rainbow Six Siege and Shadow of Tomb Raider get an even bigger boost of around 30%.
The benefits of a MUX switch aren't just limited to improved graphics performance. It also lets you experience features like NVIDIA G-Sync or higher refresh rates, which are not available with Optimus even when the laptop's dGPU supports them. But, of course, the laptop display also needs to support these features before you can use them with the discrete GPU mode.
If your laptop has a MUX switch, you'll find a Discrete GPU mode, Dedicated GPU mode, or a toggle to disable the hybrid (MSHybrid) mode in this software application. If there is no such option, you can contact the manufacturer to confirm. Unlike other manufacturers, Dell and Alienware laptops typically have hybrid and dedicated GPU mode settings in their BIOS or UEFI settings screen.
Also in Windows Settings - Graphics you can have Windows specify which GPU you use for run specific programs.
"High Performance" means the dGPU will be used and not the IGPU
"Power Saving" means the iGPU will be used instead of the dGPU.
In the past, AMD Settings used to do this function but now it is done in Windows Settings instead.
