Decided to install the latest BIOS version (86.06.39.00.62) like recommended after entering my serial number but ever since, my fans go absolutely nuts when I launch games. Any way I can fix this or is there any way to rollback to the previous version? 
 
Help would be appreciated

Download the original vbios from here. Flash the original back with nvflash.

thank you, I'll try this out and I will report back

Is there a simple tutorial I can follow for this? I'm scared of screwing up

This should be helpful...
 
Flashing procedure for single cards:

#1 Move the "980Ti-SC-425-1281mv.rom" vBIOS located inside the 980Ti-SC-425-1281mv folder into the nvflash folder via drag and drop. 
#2 Run command prompt via administrator. 
- Windows 7: Press the start button and type "cmd", right click "cmd" and select run as administrator.  
- Windows 8/10: Press the Windows Key & X keys together, right click "command prompt" and select run as administrator. 
#3 Type the following commands into the command prompt... "cd  c:\users\<your users name here>\desktop\nvflash" without quotes and hit enter. 
- Type "nvflash --protectoff" without quotes and hit enter. (Turns off write protection on the card. Some cards will need to have this disabled before you can flash the card so always perform this command before flashing.) 
- Type "nvflash -6 980Ti-SC-425-1281mv.rom" without quotes and hit enter. 
#4 If you get an error stating "Firmware image PCI Subsystem ID <xxxx.xxxx> does not match adapter PCI Subsystem ID <xxxx.xxxx>" just ignore the error (this error will cause no harm, it's just letting you know you are changing the subvendor on the card.) and continue on flashing by pressing "Y" to override the error. nvflash should now start to flash your modded vBIOS to the card and complete by saying the flash was succsessful. 
#5 Restart PC. (NVIDIA drivers should automatically detect and install the card, if not, you may need to uninstall the drivers and re-install them.)

I'm following the steps but I keep getting "ERROR : No longer supports WoW64 flasher."

Try typing nvflash & nvflash64.

Thank you. Would you recommend doing a clean drivers install with DDU after rebooting my PC?

It wouldn't hurt to do that.

Another thing, why does it recommend to update my VBIOS when I enter my serial number? Aren't the acx 2.0 cards free of issues? It also recommends the thermal pad fix