Why are you wanting to "get in to the bios" on your RX 570? It's not as easy as opening it up and looking around like you do with your motherboard; which actually most people call the cmos the bios when referring to motherboards.
For your GPU you have to save the bios file with ATIWinFlash and then open it with Polaris Bios Editor. Then, if you wanted to make changes you save the new bios file and then use ATIWinFlash to flash the bios to the GPU; it's a risky process that could result in a bricked GPU and even if it works it will void your warranty.
In short, it shouldn't be simple because it voids the warranty to alter the bios.