Just because they all come with overclocking software in no way means that they are all capable of the same overclocks. Just like anything else, the level of your OC will depend upon the quality of the hardware used ... and just because they have the same GPU, they certainly don't have the same VRMs and VRM cooling, both of which have a significant impact on the OC.
You GPU OC is limited by temps of the GPU ...we see this on the 1070 and up reference cards ... they all throttle. If we look at the original EVGA SC 1060 - 1080s, EVGA cheaped out and didn't install thermal pads on the VRM and as a result, the VRMs were overheating. In some cases they fried and EVGA came up with a BIOS fix and a thermal pad kit as a fix.
While in previous generations, these differences could be quite large, with the 10xx series however, the differences that we used to see are limited by Boost 3 ... Regardless of the components used, Boost 3 is stepping in and, to an extent, is gimping the performance that would otherwise be available with the improved components. It doesn't make the differences wholly disappear, but they will be less than we saw in previous generations.
In addition, cards with better componentry and better VRM / memory cooling will run cooler and thereby the fans won't need to spin as fast thereby creating less noise. Finally, some manufacturers will use hand picked and "binned' GPUs for their higher end lines. Now, all this being said, we still have the silicon lottery to deal with. outside of 'binned' GPU situations, it is entirely possible that you could pick a lower tiered card that overclocks better than a higher tiered card. In addition, **sometimes**, the different tiered use the exact same PCB and the exact same chip cooling methods. The difference in model price then comes from "extras" like dual BIOS, LEDs the addition of 1 click OC "modes", etc