3-pin fans are the older style and the ONLY way to control their speed is by varying the VOLTAGE supplied to them from header Pin #2. So they are called Voltage Control Mode fans.
4-pin fans are a different design called PWM Mode fans. In this system the Voltage from Pin #2 is always the full 12 VDC, plus there is a new PWM signal sent to the fan on Pin #4. The fan has a special chip inside it that uses that PWM signal to modify flow of current from the fixed 12 VDC supply line through the motor windings to change the speed. However, IF you connect such a fan to a 3-pin header it gets NO PWM signal so the chip cannot modify, BUT the Voltage on Pin #2 is now VARYING, so the fan's speed CAN be controlled this way - just no "ideal".
If you connect a 3-pin fan to a 4-pin header sending out those new PWM signals, the fan does not receive the PWM signal from Pin #4, but it has no chip so it could not use that, anyway. From Pin #2 it gets a constant 12 VDC supply, so it always runs full speed.
Today virtually all mobo headers have 4 pins, BUT in the BIOS Setup options for the headers, each can be set to use the older 3-pin Voltage Control Mode of signals, or the newer 4-pin PWM Mode. So you CAN use both types of fans, BUT you need to make them into groups - one group of 3-pin fans on a header set to Voltage Control Mode, and another group on a header set to use PWM Mode.
There are TWO types of devices used to connect more than one fan to a header, SPLITTERS and HUBS. Sellers use those names interchangeably but they are NOT the same! A SPLITTER has two types of connections: one goes to a mobo header to get inputs, and the others (two or more) are outputs for plugging in fans. ALL power for the fans comes from the header, and most fan headers can supply up to 1.0 A max current to the total load connected. Every fan should have its max current draw specified, and typically those are 0.10 to 0.25 A max per fan. So you can connect three or four (sometimes more) fans to a single header using a SPLITTER as long as you verify the max current load involved. A SPLITTER may look like a collection of cable "arms", or like a small circuit board, or like a closed box with output sockets recessed in holes.
A HUB is a different device, and it may look like any of those three types above, so you can NOT tell the difference by appearance. It also has one input (from a header) and several output connectors. BUT it has one ADDED connection that goes to a SATA or 4-pin Molex power output from the PSU. This device gets all power for its fans from the PSU that way, and draws no fan power from the host header, so the header's 1.0 A current limit does not apply. HOWEVER, the Hub supplies that fixed 12 VDC power to Pin #2 of ALL its outputs, and relays to all its fans the PWM signal it gets from the mobo host header. So a HUB can ONLY work with a header that IS using the new PWM Mode of signals, and can control the speed ONLY of 4-pin PWM fans. All its outputs provide just the new PWM mode signals, so they can NOT control the speed of any 3-pin fan.
Thus, you CAN use a HUB with 4-pin fans as long as the header it uses is set to the new PWM Mode. For 3-pin fans you MUST use only a SPLITTER connected to a header using the older Voltage Control Mode (aka DC Mode), and then you must verify the current draw of that fan group. Of course, if necessary you can make TWO groups of 3-pin fans and use two Splitters to connect the groups to separate headers, as a way to spread the load out for a LOT of fans. Note that trying to use a HUB connected to a header set to the older Voltage Control Mode will NOT work because it MUST have a PWM signal to relay to its fans. Moreover, even connected that way the Hub can NOT control the speed of a 3-pin fan that has no special chip. I am aware of ONE unusual fan HUB by Phanteks that CAN work with both header signal type and CAN control the speed of both fan types, but it is unique in these capabilities.
Every fan generates a speed signal consisting of pulses to send back to the host header, where the pulses are counted to provide a speed reading. However, the header can deal with a pulse train arriving from only ONE fan. So any Splitter or Hub will send back to the host header the speed signal from the fan connected to only ONE of of its outputs, and ignore all the others. You will never "see" the speeds of the "others" anywhere. You are to assume that those others are running at comparable speeds, although that detail varies somewhat when you connect different fan models. But what really matters, anyway, is NOT the speed, but the AIR FLOW each fan generates. In fact, the header does NOT use the speed signal it gets to control its fan(s). Its control is based entirely on a TEMPERATURE measurement, not on fan speed. BUT the header has an important second function: it does monitor that speed for NO speed, indicating fan FAILURE. If it detects failure you get a warning on screen so you know there is a problem to fix. In the particular case of the CPU_FAN header, it will take more drastic action up to shutting you down if it believes there is NO cooling for the CPU chip. This does mean that when you use a Splitter of Hub the header can NOT monitor the speed signals of ALL its fans for FAILURE, so YOU should check all your fans from time to time to verify they are still working.
In a Splitter or Hub that looks like a collection of cable arms, look closely at the output male connectors. Only ONE of them will have all 4 pins. That is the ONLY output that will send its fan's speed back to the host header. All other outputs are missing Pin#3 so they cannot send back a speed signal. For a Splitter or Hub that looks like a circuit board or a closed box, ONE of the outputs will be identified (often marked as the CPU port) as the only one that sends the speed signal back. You do NOT need to plug your CPU cooler unit into this, but you DO need to connect one fan to this port so a speed signal is sent to the host header.
OP, for you to use all (or most) of your fans, you will need to create at least two groups. One will have 3-pin fans and a Splitter on a mobo header set to Voltage Control Mode. The other can use another Splitter or Hub to connect 4-pin fans to a header set to PWM Mode. I assume all these fans are for case ventilation use, and we are NOT talking now about any CPU cooling units. For us to help you with the details, we need to know:
1. What is the maker and model of your mobo?
2. The model of that "arctic case fan hub". Does it need a connection to a PSU power output or not?
3. Maker and models of all the fans. Or at least, examine each fan for a spec of max AMP current, or maybe max WATTS of power. Tell us those specs so we can check the current limits.
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