Your mobo has two plain RGB headers on it. That is, they are of the 4-pin 12 VDC type. They are NOT the ADDRESSABLE RGB or ADDR RGB or ARGB system with 3 pins and using 5 VDC. So be sure whatever RGB lighting devices you buy, they are the 4-pin 12 VDC type.
EACH of your headers can supply up to 3A current to all the devices connected to it. Whether you use an RGB Splitter or some daisy-chain system, that limit applies per header. So you need to find the power draw specs for the RGB lighting parts only of each of your devices. For RGB strips that is straightforward. For Fans, be sure to distinguish between the current draw of the motor (NOT part of this dicussion), and the current required for the RGB lights in the fan frames. For RAM heatsinks there should not be a lot of confusion. But check carefully how the RGB lights of those heatsinks are connected. Are they really done by separate cables with standard RGB connectors, or is it done though particular pins in the RAM stick socket?