Ok so I flashed my 1080 FTW with the 1080 FTW2 bios. In order to keep the comparison apples to apples, I matched clock for clock for both GPU core and Memory. Here are my results:
It would seem that it's within margin of error but here's where the plot thickens, the new bios would pass all stability tests but when I tried to match it clock for clock with a +500 offset on the memory with the old bios I would fail almost every stress test with the exception of Superposition. I heard mention of a change in timings and that might be true but there is also a chance that the memory voltage is slightly higher.
An important note: Obviously, this didn't brick my card but I flashed this onto a 1080 FTW that is in a custom loop. There is no telling how this bios will impact an ACX cooler since it was designed for an iCX cooler with independent fan control. In other words, just because this worked for me, it may not work for you because the main distinction between an ACX and an iCX card is moot for me in this use case because I am not using the cooler or the fans.