Just mod the original saved bios on your computer and flash it to your cards , you dont need to flash the bios , then save the bios , then mod the bios, then flash the modded bios...
I think for rx 480 cards is not not the best option to copy the mem straps from from 2000 to 1750.
in my experience if you do just the mem strap cpoy paste kind of " bios mod " you should
copy 1500 to 1625 and 1750 to 2000 ,or try first just 1750 to 2000 ...
and then follow my guide 
Isn't that the timing for 4GB cards? Should I really try it with my 8 GB cards?
I wanted to follow this guide to flash my bios and in minute 1:20 the guy says there's a difference between 4 and 8 GB
https://www.youtube.com/watch?v=JKM60VVIfRg&t=5s
