Whats the point ( duo / single BIOS )

[Letharas]

What is the difference between them (that u have 1 or 2 haha) but why do u need 2?

[Mira Yurizaki]

Motherboards have two in the event your primary one gets corrupted either just because or due to a botched update. This is a good thing, otherwise you'll be left with a bricked motherboard.

[mariushm]

For video cards, the second bios is often intended for overclocking, with higher fan speeds by default, higher voltages and power limits.The intention is for the user to flash the second bios with custom code, turn off pc and flip the switch to boot using the new bios, and if there's  any problems you can quickly flip the switch and reset the pc to restart the video card from the original bios.

You can modify both bioses, it's just that what I said above is for lots of people the usual procedure, it's common.