What purpose does a capacitor before each SK6812RGBW serve?

Question

On a SK6812RGBW strip, such as this one sold by Adafruit, each segment has both an LED and a capacitor (of some unknown value). What purpose does this capacitor serve?

In this question, it was stated that the capacitor before the entire strip is to make up for the wire's inability to provide an instant, large change in current. One guess I had for the capacitors in the strip is that they provide this sort of protection in case the segments are cut apart and connected to thin wires by the user.

In this guide provided by Adafruit, at the bottom of the page, it states:

With through-hole NeoPixels (5mm or 8mm), add a 0.1 µF capacitor between the + and – pins of EACH PIXEL. Individual pixels may misbehave without this “decoupling cap.”

Since I don't know the value of the capacitor on the strip, I'm not sure if the capacitors serve the first or second purpose. Which is more likely? If I were to use sufficiently large traces on my PCB, are the capacitors necessary?

Answer 1

PCB traces have resistance which limits DC current (simply put, defines how much current is available) but PCB traces also have inductance which limits AC current (simply put, defines how fast the current is available), so the generic 100nF bypass capacitors are still necessary even with sufficiently large PCB traces.