I guess I was not clear. Certainly there ARE both SPLITTERS and HUBS that allow you to connect several ARGB lighting devices (fans, strips, etc) to one Controller output, whether that is a third party separate Controller or just the ARGB header built into a mobo. Whether you need a Splitter or a Hub depends mostly on how may lighting devices you plan to use. Any one ARGB header on a mobo has a limit of the max current it can provide to all connected lights, and a related limit on the max number of light nodes or LED's it can deal with. If you are planning many lighting devices, you MAY need to use a Hub which can provide more power.
Either way, a Splitter or a Hub can only distribute to ALL of its devices the SAME control signal. For example, if you have three fans with lights in their frames plus one light strip all on a single Splitter and mobo ARGB header, all of those items will show exactly the same display pattern at any moment. On one fan at one moment the pattern may be a single colour, one colour in different brightnesses, a rainbow, etc. - all of the possibilities of an ARGB display. But every fan will look exactly like that at that moment, and as your display changes they ALL will change the same. The only way to have different fans display different light patterns is to have them fed from different Controllers (or mobo headers) that are programmed to do different things. In your case, OP, your mobo has TWO ARGB headers, so using the MSI Mystic Light utility you CAN make each of those headers put out different signals. That way you could create TWO groups of lighted fan frames, and each group can be different from the other. But within one Group all fans would look the same at any one moment.
The new Gen2 version of ARGB lighting I mentioned above changes those limits. It appears what they can do is treat up to four light devices (fan, strip) separately on one circuit (mobo header and Splitter) so that each device (one fan) is controlled separately from the others. The result is that you could connect four fans via a Splitter to one mobo header and all four fans' displays can be different at any one moment. This takes a bunch of work to create the configurations for the fans, but is allows more diversity in your displays than the normal ARGB system. Again, I know on only two companies right now - ASUS and Cooler Master - who sell devices for this new Gen2 system.