OK, so you're planning to use Corsair H75 AIO system with a pump unit, a 120mm radiator, and a pair of 120mm PWM-type rad fans in a push / pull arrangement. First, let's ensure that this is kept simple. You are creating an AIO cooling system for the GPU chip of your graphics card. Although you are using components often used for main board CPU or for case cooling, this system has virtually NO link to those other two cooling systems. So keep it separate from the CPU and the case fan systems.
You have a way to remove the fans and their mounting system that come on the graphics card, and probably also the heat exchanger (fins) on that GPU chip. Then you will have to mount the pump unit from the H75 system on the GPU chip with appropriate thermal paste, and use the Kraken G12 system to fasten that into place securely. In doing so you also will use the Gelid adapter cable to provide a lead out from the graphics card's normal fan header, and will further plug into that the cable from the Hub that normally goes to a mobo fan header. This will make the Hub control its fans according to whatever the graphics card's fan control system wants, with no link to any mobo factors.
The H75 pump unit will need a fixed +12 VDC power supply, and it has a cable from it ending in a 3-pin female (with holes) standard fan connector. This can plug into any fan header that can supply a constant 12 VDC on Pin #2, and Ground on Pin #1. This line also will send its own pump speed signal out on its Pin #3. We do not know whether the fan header on the graphics card does any monitoring of the speed of its fans for failure, but it may. So, I suggest the best place to plug in the PUMP's 3-pin fan connector is to the one port of the Silverstone fan Hub that is specially marked. This is the only port of that Hub that can send its speed signal back to the host header (on the graphics card). Now, the Silverstone Hub gets its power from a connection to a SATA power output connector from the PSU, so its pump and fans do not draw any power from the host header on the graphics card and cannot overload that header. Because it is designed to operate only in a 4-pin fan system, it always supplies on every one of its output ports a Ground on Pin #1 and +12 VDC (constant) on Pin #2. Thus plugging the PUMP into a Hub port does guarantee it gets the correct power supply. And when you plug it into Port #1, then the pump's speed will be relayed back to the graphics card's fan header via the Gelid adapter cable you connect between the card and the Hub's fan input connector. Since continued operation of the pump is vital to GPU cooling in your system, giving that speed signal to the graphic card's fan header will allow it to monitor for cooling failure IF it is already set up to do that. THEN the two fans mounted on the radiator of the H75 system can be plugged into two other ports of the Silverstone Hub, and their speeds both will be controlled by the signals from the graphics card's fan header. For your info, note that there is NO way for any item here to monitor those two FANS for failure, and no way for you to "see" their speeds. From time you time you should just check to be sure they both are still working.
When you set things up like this, the H75 is a cooling system for the GPU chip in the graphics card, and nothing else. All power for the pump and fans of this system will be drawn from the PSU. The pump will have the constant full 12VDC power supply it needs and its speed signal may be monitored by the graphics card for failure IF the card actually is designed to do that (we don't know). The speed of the two radiator fans will be automatically controlled by the graphics card itself, based on the temperature inside the GPU chip.
Since there is no connection between this H75 system and the mobo, you will NOT ever see any info about it in BIOS Setup or any mobo cooling system utility software tools. SOME graphics cards do monitor their GPU temperatures and cooling fan speeds and MAY make these pieces of info available through their own graphics card optimization software tools. If yours does, just remember that what it reports to you as the FAN speed cooling the GPU really will be the PUMP speed of the H75 system you have installed.