Your small confusion is normal. Like similar utilities supplied by other mobo makers, the ASUS Aura Sync tool can be used with both 3-pin (5 VDC ADDR RGB) and 4-pin (12 VDC plain RGB) lighting systems. That's because mobos are made with both type of headers. Is is designed to work with either type of mobo RGB header, so the name of the utility does NOT tell you what type of lighting device you need. You need to match your RGB lighting devices (including those mounted in a fan frame) to the type of header you have available on your mobo. To do that, look carefully at the specs of the fans you consider, and at their photos.
First, specs. RGB fans all come with TWO cables to them - one for the motor, ending in a standard female 3- or 4-pin fan connector, and another ending in a larger female 3- or 4-pin RGB connector. The specs should say clearly that these are either RGB lights or Addressable RGB (aka ADDR RGB or ARGB) lights. They may also specify that they are for either 12 V or 5 V systems: the plain RGB are the 12 V systems with 4-pin RGB connectors, and the ADDR RGB are the 5 V systems with 3-pin connectors. Sometimes the specs also caution you to connect only to the correct type of RGB header. (Although the LED's involved all actually use 5 VDC on their leads, that detail is normally ignored in the specs and you are only told they need either a 12 V or a 5 V connection.)
Secondly, illustrative photos. In a plain (4-pin 12 VDC) system all of the lights in the entire lighting unit (one fan) will be only one colour at any moment, although that can be changed to another later. In the ADDR RGB system, one device can show many different colours along its length at the same time, so you will see photos showing a rainbow of colours around the ring of the fan to emphasize this feature. That can be a big clue, easy to see as you scan though web pages. Using that you can focus in on the type you are looking for and then confirm by examining specs.