Huh, weird. Have to check that out, I'm really curious how they can manage RGB and three fans via a daisy chain with a fan header.

I guess they just made a separate bus that is controlled via that USB dongle and each fan has their own ID.

This has existed for digital battery monitoring systems (BMS) for quite a while (including those in Tesla cars), in which each battery in a chain can be inspected through a single wire that goes to all of them. Obviously, it's a digital signal.

I'm personally not fond of this. It appears to use a PCIe power source, but I'd much rather it use molex, SATA, or the old floppy connector. Nowadays people have way more of those connectors than they know what to do with, meanwhile it's common to find people needing more PCIe connectors. These aren't high-speed fans, they don't need the amperage to warrant a 75W connector. Also, most modern motherboard fan controllers are pretty advanced and configurable (and many can be manually operated in your OS). I'd much rather have a smaller power brick, not bother with 3rd party software, and have the motherboard control the speed. For boards that need to read the RPM, you just have to connect the tacho of one of the fans to pin 3 of the fan header and you're good. They're all the same fan so they ought to all run at the same speed. For my PC, I built my own fan controller that pretty much does what I just described and it cost me less than $1. All you really need is a resistor and an NPN transistor and you can control as many fans as you want using pin 4 of the motherboard fan header. Doing this is also great when you want to control a 2 or 3 pin fan via PWM (which applies in my case). EDIT: If anyone wants to know how to build their own "3 to 4 pin fan controller", techpowerup has 2 forum posts, one called "So you want PWM control of your new CPU fan?" and the other called "So you want PWM control of your 3-pin fan?".

I'm personally not fond of this. It appears to use a PCIe power source

No, it doesn't use PCIe power. It uses a 6 pin connector to the fans from the controller. The controller is supplied by a 4 pin connector. The other end of that 4 pin connectors looks like it's a SATA power connector.