Testing the block for thermal performance is fairly simple once you realize that you have to measure VRM temperatures manually. As such, I installed an Omega NTC type thermistor on VRM 1 and connected it to an external display for a VRM temperature readout. TechPowerUp GPU-Z was used to monitor GPU core temperatures. The GPU was overclocked to 2 GHz, although with how GPU Boost 3.0 works, it did vary by +/- 1 clock bin (13 MHz). Similarly, with the core voltage being almost impossible to set manually and affix at that point, it is best to compare the results below within the data set and not with other reviews elsewhere. For what it is worth, 1.07 V was set at Vcore using ASUS GPU TweakII.
Everything required was placed inside a hotbox, and the ambient temperature was set to 25 °C. Gelid GC-Extreme was used as the thermal paste of choice since the Bykski block did not come with TIM included, and cure time was taken into consideration. Three separate mounts/runs were done for statistical accuracy and to remove chances of any mounting-related anomalies. For each run, a 60 minute Unigine Heaven 4.0 run was done, and temperatures were monitored until a steady state was reached, after which they were recorded. A delta T of GPU core/VRM and loop temperatures was thus calculated for each run with an average delta T that was then obtained across all five runs. This way, the cooling solution is taken out of the picture.
There are two separate things to take note of in the first graph. First up is the block-to-block comparison wherein I will say again that the relatively worse contact I had with the Bykski block may well have been a factor. The difference is within 1 °C regardless; however, EKWB with their years of experience and direct contacts with AICs, including ASUS, have here a block that fits perfectly and worked very well. For some context, the stock cooler at these conditions throttled the clock to 1944 MHz eventually, or near around, and at >70 °C vs. the ~46-47 °C here, so I suppose the winner really is you who decided to watercool the GPU.
The second point here is the effect of the EKWB GPU backplate, wherein the use of such a metal backplate with thermal pads to aid in heat transfer further brought down the GPU core temperature. In fact, the drop with a backplate included was larger than the difference between the two blocks themselves, so hopefully, this confirms that a well-designed backplate can be an item of form and function alike. The stock backplate, however, is an insulators and will end up potentially hurting thermal performance rather than helping it.
The story is the same with the VRMs, wherein the absolute numbers are higher, which results in the differences between these three test cases being higher as well. The trend itself remains the same, however, with the EKWB block and backplate combo taking top place here. Practically, the actual differences here do not matter given how locked-down the platform is, so these are better as an indication of how other GPUs where cool VRMs have a larger effect will benefit from watercooling.