it can handle 4 fans for PWM, but it can only drive 2 fans for RGB, because AC controllers are 90 LEDs per channel, and each QL fan is 34 LEDs.
So you will more likely need an Octo + a farbwerk360 (4 channels RGBpx).
PWM on Octo, RGB on Farbwerk.
ALso, the Farbwerk RGB is more advanced, you can stack up effects and play with transparency between effects(as you could with Corsair controllers). Octo doesn't do that.
Whenever someone uses QL fans it's a bit more complicated because they fill up RGB channels quickly so you have to use more Splittys, even tho it's not needed on the PWM side.

The Corsair QL Fans use 34 LEDs each.
The Aquacomputer RGBpx System is limited to 90 LEDs for each RGBpx Channel.
If you want to control the LEDs with Aquasuite Software, you can only connect 2 QL Fans.

If you only want to control the Fan Speed, and use the Corsair Commander for the LED Control, you can connect up to 4 Fans.

Please note:
The RGBpx Splitty4 is a passive PCB, that serves as a Y-Cable for Fan and LEDs. It does NOT have the ability to control things.
You always need a dedicated Controller for the Splitty4 to work. (e.g. Quadro, Octo, D5 Next, Farbwerk360, etc)

Quoted from "Hufeisen"

The Corsair QL Fans use 34 LEDs each.
The Aquacomputer RGBpx System is limited to 90 LEDs for each RGBpx Channel.
If you want to control the LEDs with Aquasuite Software, you can only connect 2 QL Fans.

If you only want to control the Fan Speed, and use the Corsair Commander for the LED Control, you can connect up to 4 Fans.

Please note:
The RGBpx Splitty4 is a passive PCB, that serves as a Y-Cable for Fan and LEDs. It does NOT have the ability to control things.
You always need a dedicated Controller for the Splitty4 to work. (e.g. Quadro, Octo, D5 Next, Farbwerk360, etc)

OP could use a Commander Pro and 2 Corsair RGB hubs, but if he bought the QL120 fans in 3-packs, they come with a Lighting Node Core. Each Lighting Node Core can handle 6 x QL fans, so OP would need 2 of them. Using Corsair controllers unfortunately means using Corsair iCue, or OpenRGB, or one of the other RGB utilities that can control Corsair RGB controllers. If OP wants all RGB under Aquasuite control, he will have to install 5 x Splitty4s. If OP is OK with using Corsair iCue or whatever Corsair compatible RGB control program, then using the Lighting Node Cores is the least hardware intensive way to do it.

I have 7 QL fans in my rig. I am using 2 x Lighting Node Cores and controlling them with SIV (NOT iCue). My pump LEDs and all of my RGBpx LED strips are controlled by Aquasuite via 2 x Farbwek360's. Motherboard and RAM RGB is controlled by Open RGB. It's not optimal since I still have 3 different programs controlling lighting, but at least I have managed to eliminate iCue and Asus Aura & Armoury Crate. I refuse to install any of those programs. Aquasuite RGB control is very nice to work with, and offers some great presets that the user can heavily modify. That said, there are things that I can do in iCue that I have not been able to replicate or eve get close to in Aquasuite. I like those effects, but not enough to install iCue on my system. Another thing I have discovered is that if you have multiple Farbwek360's running, there does not appear to be any synchronization between them, so you have to be careful about how you group things.

Good luck and please do post your progress. Always interested in the solutions people come up with for RGB control. Unfortunately, the RGB craze evolved in a rather haphazard way, resulting in a free for all of RGB hardware and software.

You need:
1* Octo
1* Farbwerk 360
5* RGBpx Splitty4

and two free USB2.0 ports on your Motherboard. If you dont have enough internal USB Ports, you can buy a Hubby7.

All required cables are included.

actually, the octo and fatbwerk use half a header each, so they can work off one single header. just watch the pinout

maybe check on the shop how many RGBpx cables come with splittys and Farbwerk, to make sure you have enough. apart from that it looks good

Your list looks correct to me (FWIW).I don't blame you for not wanting to install iCue. I am guessing you have already been down that path.

Thinking this through, if I have this right, you will have 5 x Splitty4's but only 4 RGBpx ports on the Farbwerk360. You could connect the RGBpx of the 5th Splitty4 to an RGBpx port on the Octo, but Octo RGBpx ports are more limited than the RGBpx ports on the Farkwerk360. The other option is to do what I did and get a 2nd Farbwerk360, then connect the RGBpx port on the 5th Splitty4 to an RGBpx port on the 2nd Farbwerk360. Note that the Farbwerk360s operate asynchronously, which could be an issue depending on what RGB effects you will be using. Also note that the Farbwerk360 comes with 2 x RGBpx cables #53287 (50cm) and 2 x 15-LED RGBpx LED strips. The Splitty4 comes with 1 x 50cm RGBpx cable and 1 x 70cm 4-pin PWM fan cable, so you are covered for PWM fan and RGBpx cables.

Other stuff to consider ordering:

If you end up adding a 2nd Farbwerk360, you need another USB port to plug it into. All of their USB cables are 5-pin at the USB header end so you can get 2 of them on 1 USB10-pin port. I would just add a Hubby7.

You might want to throw in a couple of Aquacompter #53282 adapters. These little guys come in handy if you want to connect an RGB device that has the standard ARGB connectors on it to an Aquacomputer RGBpx port. I used one to connect the LEDs in my Fractal Celsius+ RGB pump to a Farbwerk360 port. They also have the opposite adapter #53285 that allows an RGBpx device to be connected to a standard ARGB +5VDC mobo port (or whatever).

If you have need of these adapters, you will also need RGBpx cables to connect to these adapters. These are actually just Molex Picoblade connectors, so you can buy the parts to make them yourself if so inclined. Molex also has pre-made cables but I think the standard pinout is different than the Aquacomputer pinout. Easier to just buy the Aquacomputer RGBpx cables unless you will be using a lot of them. Unlike Corsair, Aquacomputer provides these adapters to allow interconnecting their RGB devices to other products. Maybe if Corsair had more confidence in their iCue platform, they would not make it all a closed proprietary system with no provision to connect a non-Corsair RGB device.

you can't stack effects on Octo and Quadro.
On Farbwerk, you can set multiple effects to work on the same LEDs with transparency. Like, set a background effect, and add on top other effects etc..

Here is what I know, from the operation manuals for the Octo and the Farbwerk360. Each LED preset can be customized in various different ways, and assigned to some specific number of LEDs. You do this by adding "LED Controllers" in Aquasuite. There is a limit to how many of these LED Controllers you can have. On the Farbwek360, the limit is 20, total, for all 4 RGBpx ports. On the Octo, the limit is 6 LED Controllers for each RGBpx port.

The other difference is Transparency. With both the Farbwerk360 and the Octo, you can "stack" LED Controllers so that more than one effect is assigned to the same LEDs. The top ones get priority over lower ones. With Octo RGBpx ports, the colors in the RGB Controllers are considered "solid" so a higher level controller will completely occlude lower controllers. With the Farbwerk360, you can assign levels of Opacity. so lower level effects can "bleed through" the higher level effects. I feel like I am not explaining this clearly and suggest you read the User and Installation manuals for both. The Octo limitation of 6 concurrent LED Controllers per port is stated in section 11.1 of the manual. For the Farbwerk, the 20 LED Controller limit is stated in section 10.1. Transparency is section 10.7 (Farbwerk360 only).

There may be other differences that I am not aware of but these are the main 2 things that I know are more limited on the Octo. They may make no difference to your RGB plans at all, but if you are planning to set up multiple effects that are concurrently assigned to the same group of LEDs, the Farbwerk360 Transparency feature allows things that are not possible with the Octo. If you are just planning on solid colors or single level effects, the Octo RGBpx ports will be all you need.

you can achieve that effect with the Scanner or Laser effect in one go.
laser goes in only one direction, while Scanner goes back and forth.

Now if you want to animate a bit your blue background (like a flame flicker in blue) you will need to stack effects

Glad to see it worked but I was planning to use QL120: why do you want to change?

Not OP but guessing he was disappointed with the QL-120 performance. They look great (I think) but Corsair spec for static pressure is only 1.5mm H2O. Airflow is 41.8 CFM. The Lion Li SL120 spec says static pressure is 2.54mm H2O and airflow is 58.84 CFM. So higher static pressure and more air flow. Corsair does not make an RGB fan with 2.54mm H2O of static pressure. Even their SP120 only does 1.46mm. The old HD120 (single color) fans do 2.25mm. This all presumes that you can believe any of Corsair's specs. If your main criteria for a fan is performance, the QL series are not good choices. If you main criteria is how many LEDs they managed to cram into a fan, the QL series are great. Unfortunately, the 90 LED limit on Aquacomputer RGBpx ports does not divide well by 34 LEDs per QL series fan. Hence OP's need for so many Splitty4s.