I have no personal experience with the Corsair H100i RGB Platinum system. As far a fan performance goes, I consider the Noctua products to be among the best, so I tend to use them as a best-case comparison basis. Typically they deliver high air flow against good backpressures with low noise, and are well built to last a long time. Of course, Noctua do NOT have any RGB fans, so a direct comparison with the Corsair ML120 PRO RGB LED line is not exactly the same. But given that, the ML120 PRO RGB units have slightly less performance (air flow and pressure max's) and slightly higher max noise than a comparable Noctua unit, but still quite OK. And those Corsair fans come with a 5-year warranty, close to what Noctua offers and much better than many lesser fans.
I agree that it appears that the Kraken K52 system has lighting in the pump portion only, and none in the fans it includes.
Regarding using the Corsair system to add to your lighting effects, it depends a great deal on other details of your case and how it is assembled. The fans on a Radiator show very little light through the rad. So IF they are mounted on the INSIDE of the rad, their light is directed into the case. Now, if you have a case with a big open transparent window on its side, that may show the lighting effects depending on where your case it placed. The options for directly exposing the RGB fans to the exterior of the case really come down to mounting the fans on the OUTSIDE of the rad, and then that involves air flow direction and balance. Many people want to place INTAKE fans in the case front, and one way to do that is to mount your rad there with the fans outside the rad drawing outside air into the case and blowing it over the rad. This does that job. Then it is often advised that the case have an EXHAUST fan at the rear, and that often does NOT have lighting in it because it may never be seen. For some, that's enough air flow, and gives reasonable balance. Ideally (I believe, although others may differ), you should have slightly more air flow capacity as Intake over Exhaust so that the case has a small positive pressure inside, and any air leakage through cracks flows inside to outside, preventing inflow of dust. And that also means that the Intake fans really need to have dust filters on them to keep out the major airborne dust source. So more intake fans than exhaust fans is a ROUGH way to ensure that balance. Taking into account that the radiator AND the dust filters both restrict air flow through any fan, a pair of fans with dust filters and blowing though a rad on the front will not cause as much air flow as two unrestricted fans, but surely more than one unrestricted rear fan, so appropriate balance is likely in this arrangement.
Now, many people think that is not enough air flow, and want to add more fans on the top. It is often recommended that the top fans be directed for exhaust. In fact, that's another way to arrange a rad and fans. Put the rad on top with the fans INSIDE it and blowing warmer air from the case interior out through the rad. Then mount intake fans in the front instead of the rad system. But if you do that, the air through the rad is warmer than outside air so the cooling effect is reduced, and many would prefer to make a top-mounted rad an INTAKE to improve on that. Simply mounting the rad and fans that way on the top instead of on the front would achieve that and establish much the same air flow balance as before, but it does not add more air flow. And that MAY not expose your RGB lighting as well as a front-mounted system.
So how do we get more air flow (IF you consider it needed)? One arrangement many like is to do the rad system in front, single exhaust fan at rear, and two added fans in the top for exhaust. To my way of thinking that creates an airflow strongly pushed toward negative interior pressure. Simply switching the top fan pair to intake makes too much intake capacity, I think. Personally I would prefer front rad (and fans) intake, single or double rear exhaust, and one added intake fan in the front IF there is space, or in the top. IF there is space on the rear for a second exhaust fan, then two added intakes (front and / or top) would make some sense.
Anyway, that's my design thinking. You may disagree on some of my preferences, and that's up to you - it's your system! And I realize that this has gotten more complicated, moving from simply adding RGB lighting, to fan and radiator placement for maximum visual appeal as well as balancing air flow and dust intake, etc. Further, if you were to consider adding more than the two ARGB fans that come with the Corsair H100i system, where would you plug in their ARGB lighting components? But of course you might not do that - you already have some fans with Phanteks frames that use the plain RGB system from your mobo header, and that is part of your air flow balance and placement thinking.
Have fun figuring this all out!