OP, responding to two points raised.
So the user comment you cited on Amazon says he found a connector on the video card that apparently looks and acts like a standard 4-pin fan connector. It may or may not be using the new PWM Mode for speed control, but that does not matter if it works. A small point to consider there. Almost all mobo fan headers can supply power up to 1.0 A max total load. The combined load of the two rad fans plus the one for VRM cooling on the card is 0.66 A, quite acceptable for that limit. The only item not yet known for sure it whether the system on the VIDEO CARD actually has that same ability to supply up to 1.0 A max. Note that, to power these THREE items from one video card fan header, you'll need a 4-pin SPLITTER with at least three outputs, like this
https://www.amazon.com/Cable-Matter...keywords=4-pin+Splitter&qid=1617121377&sr=8-3
That's a 2-pack. In using that, note that a fan header can deal with the SPEED signal from only one fan, so the Splitter will only send back a speed signal from one of its outputs. There is no way to check the speed of the fans on the other outputs. On a Splitter, that normally is from the fan that is plugged into the ONLY output arm with all FOUR pins. (On the item linked, it comes with a label on that arm.) Among the three fans you will connect, I suggest you plug into that output arm the VRM fan on the card. This is because I assume (may be wrong) that the video card will do a secondary job at that fan header similar to what a mobo header does: monitor the speed signal it gets for possible FAILURE of the fan, to protect itself from overheating. Among those three fans, the on-card VRM cooler is more important for failure detection, because a failure of one rad fan will only result in a slow temperature rise on the card, not a rapid problem.
For power supply to the PUMP, there are a few details to consider. First, until ID Cooling replies, you don't know for sure what power the pump needs. In AIO cooler systems for a CPU chip, often the pump uses a connection to a 4-pin header that is using the new PWM Mode of fan speed control. This works because they are using a quirk of fan design: the pump is wired just like a 3-pin older fan type, and connecting that to a standard 4-pin PWM header means the pump ALWAYS gets a full 12 VDC power supply and runs full speed, which is how it is intended to run. That MAY be how this pump is wired and designed. If so, then it is important to know what else is plugged into that SYS_FAN header, and how it is configured. IF that header has a 4-pin fan and IS configured in BIOS Setup to use the new PWM Mode, then this all can work. (To check that detail, look in your mobo manual on p. 16 in the inserted graph. At upper left it should be set to PWM, not DC, for this to work. BUT if you have changed that to accommodate an older 3-pin fan on that header, there is a problem. Of course, if you are going to do this you will need a 4-pin Splitter to power both the video card cooler system pump and a case fan from it. You nay even have such an item in use now - depends on how your case cooling is done. If you already have more than one fan attached there, remember that you are proposing to add 0.25 A extra load on that header. ALSO, if you do this, again I recommend plugging this PUMP into the ONLY Splitter output that picks up the "fan" speed signal to monitor for failure. For video card cooling, continued functioning of that pump is critical, so you want to be warned of failure. You just have to remember that, if the mobo tells you the CASE fan (SYS_FAN) has failed, it really it the VIDEO CARD PUMP that has failed and needs immediate attention.
IF you cannot arrange properly to supply power to the pump from the SYS_FAN header, and IF you find out that ID cooling says the pump needs a fixed 12 VDC power supply, that CAN be done using an adapter designed to allow you to connect a 4-pin fan directly to a power output from the PSU.
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