After reading and watching various stuff online, I thought I should share my own experience.
How I ended up with them
Some background: First, there was no plan when I bought the 2080Ti (in September), so in retrospect, I probably wouldn't buy the non-A model again; then, water cooling was never on my mind when choosing the case (MSI Mag Vampiric 011c), which is another thing I would've done differently.
As you know, the stock cooler is pretty loud when the GPU's running at full load (about 2800 rpm at 70% speed) and the 112% power limit is quite annoying, so I flashed in the Palit BIOS to get that extra 12% power, but the fan speed range is borked. Before you ask, yes, I considered the shunt mod, but it's too adventurous to me because EVGA's generous warranty is a big reason why I chose them.
Google took me to Reddit, here, [H]ard, Youtube and other places in my search for an appropriate solution and it ended up with AIO cooler. Even though my case limits my choices a lot if I want to use custom loop, but I actually came up with a configuration that would work. I didn't go that route because:
1) It's kind of expensive although my config only costs ~US$ 400 converted;
2) Custom loop is too much work as I don't enjoy tinkering with my PC all the time;
3) It's more prone to fail since it's a lot more complicated, especially risk of leakage.
Of course, there are aftermarket air coolers, but I didn't find any particularly good one.
So, why Krakens? Because people already tried them and NZXT has a proven software to control the cooler, which, I think, sort of justifys the price tag. There's also a vendor that makes full aluminum AIO adapters for GPUs at a pretty reasonable price, but they don't have my model measured, so I would have to send them my card. If my case didn't limit my choices, I would've gotten an x72. In the end, I bought a second hand x52 for less than half of the retail price.
You may be wondering how G10 fits. Well, I mounted G12 with G10's backplate while keeping the original backplate as is on the card.
Why this way? Because I want to spread the pressure on the whole PCB as much as possible. It's probably 10-layer, but those thru-holes don't exactly give me confidence due to G12's AMD brackets not fitting in as shown in this thread
My solution is to file off top threads by ~1.5 mm:
and bottom plates' edges by ~2 mm:
Special thanks to my father for the metalworking and finding the M3 screws and nuts below.
The screws fit in the G10 backplate like this:
Yes, the text is upside down, but it's blocked off after installing in the case, so I didn't bother rotating it. The ideal length of the screws would be 15 mm.
2 other things worth mentioning:
1) I used anti-vibration mounts on G12 for the fan, but it turned out there's not enough space at the molex connectors, so I ended up using only 3 rubber sticks.
2) G12 wasn't designed for inductors on both sides, so I used a PCI fan bracket to mount another 9 mm fan on the left.
Temperatures and Benchmark
Precision X1 suggested +139 after scan, not as high as original BIOS's +145. I launched Furmark's stress test when I started typing this post. This is 2 hours later:
Port Royal auto overclock: https://www.3dmark.com/pr/177366
and manual overclock: https://www.3dmark.com/pr/182015
Also, the thermal paste I used initially has a rated conductivity of 6.2 W/(mK) which I find to be lacking since GPU and liquid temperature can differ up to 10 C, maybe more. The paste I'm using now is rated at 14.3 W/(mK) that kept the temperature difference within 8 C.