From the looks of things, about a third of the airflow do not even reach the heatsink. Also, a lot of the heatsink probably gets no airflow. Genius. Guess what happens if all the airflow from some Noctuas are forced through the entire heatsink? (spoiler: I know what happens)
If you live in proximity of Oslo Norway, or is willing to pay for shipping your card round-trip to me, I will be happy to make a you a free 3D-printed duct for your GFX. I will then sell copies of that duct, or license it for printing for 3$ a copy.
Using 120 A25, expect about 700rpm for a rx 6600 xt. Using stock D15 fans, expect 450rpm for a rx 6600 xt. That gives you about the same temps, as a stock MSI gaming X rx 6600 xt @1400rpm. Just be warned, as we all know by now, the stock D15 fan has a faint low frequency hum to it. Using the 120 a25, you will get all that wonderful VRM noise, as VRM noise will completely dwarf the fan noise, but at least for my current copy, it is really not that bad at all. Best GFX VRM I have ever had, and I have had a few low noise setups by now.
In case you missed it. Using two 140mm noctua fans, I cool my MSI Gaming X rx 6600xt @ about 450rpm vs stock @ about 1400rpm. But you will not get anywhere near that, with the duct used in the article images.
If you want RGB, lets just say that this is the better disco. You can pick any RGB fan you want, and almost any 14cm RGB fan and most 12cm RGB fan, will outperform a stock fan on noise.
I sort of have no fan noise issue anymore, as my PSU runs semi passive, and my case is a custom design without any case fans. Funny what some pieces of plastics can do, if you know what you are doing. Going live with this shortly.