Wow, you're "on your own" with that mobo with no manual. Its website says they ship various versions that keep changing. So all we can offer is advice based on what is "normal" for mobos.
I could not spot the fan headers in the photos, so I''ll take you word for it that it probably has two 4-pin CPU_FAN headers and maybe two 3-pin headers labelled EITHER CHA_FAN or SYS_FAN. Alert: for the case ventilation fans that connect to the 3-pin headers, do NOT buy 4-pin fans. They would work, but they just cost more than similar 3-pin models.
GENERAL rule when connecting more than one item to one fan header is that the header can supply up to 1.0 A max current. When using a SPLITTER for this, all the power comes from the header, so that limit applies. NOTE that sellers mix up the labels Splitter and Hub, but I prefer to use the words this way. A SPLITTER is simple with only two types of connections: one input from a mobo header, and two or more outputs to fans. A HUB has these PLUS a third "arm" or edge connector that must connect to a power output (either SATA or 4-pin Molex) from the PSU for all the power to the fans, and this unit does NOT get fan power from the host header. For what you are doing, a SPLITTER for each CPU cooler system is sufficient.
Your concern about header overloading is worth considering, but the result is no problem. The web page for that cooler system's manual is here
https://bucket-zv5zpj.s3.ap-northeast-2.amazonaws.com/manuals/AQUAELITE120V3.pdf
On its Page 12 you can see details of making connections for the pump and fan motors and for their ARGB lights except they do not show the pump connection clearly. But NOTE that for one system there are two fans and one pump to connect, and the Splitter unit they include (the call it a "hub" which I say is wrong) has three output ports. So you CAN connect all three to one CPU_FAN header. Important item to do when you plug things in. The Splitter box has labels on it so ONE may tell you to plug in the PUMP there. If not, you may find that only one has all four pins in the output, and the other two are each missing Pin #3. Either way, ONLY that one port can send back to its host header the speed of its "fan". It is IMPORTANT that you plug into that one port the PUMP so its speed can be sent to the header. Why? Well, all CPU_FAN headers do an important second function: the monitor the speed of the "fan" attached for NO speed, which indicates failure. In any AIO system, the vital item to monitor for failure is the PUMP, so that is the speed that needs to be connected to the CPU_FAN header, and that is the unit whose speed can be shown to you by BIOS Setup. The speed of the two fans plugged into the two other ports of the Splitter will never be seen anywhere.
In terms of electrical load, the specs for that AIO system say the PUMP consumes at max 4.8 W at 12 VDC, which is 0.40 A. Then each FAN can consume at max 0.20 A. So total is 0.80 A, less than the header limit, and hence safe to do.
Now here's the "trick" to this. In almost all AIO systems the pump is intended to run at full speed all the time, so that control of CPU temperture is done only by varying the speed of the rad fans. The pump is wired just like an older 3-pin fan, so when you connect it to a header sending out control signals in the new 4-pin PWM Mode, that fan (well, pump in this case) will always run full speed as intended. On the other hand, the 4-pin FANS on the rad WILL be speed-controlled by such singals. IF you have an option in the configuration details of each CPU_FAN header, make sure each is set to use PWM Mode, and not DC or Voltage or Auto.
If you make your connections this way for each of the AIO systems on their separate CPU_FAN headers, you have the pump and both rand fans connected to a single CPU_FAN header. The pump will run full speed always as designed and will report its speed to the header to be monitored for failure. The rad fans' speeds will be controlled by the header according to the temperture measured by a sensor inside each CPU chip, but you will noever see those fan speeds anywhere. YOU should look at them from time to time to be sure they all are still operating.