The first splitter moves two of the wire pairs as mentioned by another person to make use of the two pairs that are not normally used in a 10/100 network. Gigabit uses all 4 pairs...
The EtD puts one pixelnet universe (or dmx universe) per wire pair.
The second splitter is a simple Y connection. Every time you split, you degrade the signal. You should be able to use 1 of these without too big an issue, just keep it close to the EtD end.
If you cascade them - split a split, you are just asking for trouble. You might get away with it, you might not. You might get away with it today, and it not work tomorrow.
We want you to have consistent performance, not continuous frustration.
Why? Each split creates an impedance mismatch, which creates a reflection in the signal much like a glass to air boundary does to light. Using light as an example, shining a flashlight through a window pane gives you a reflection. Shining that same light through a double paned window gives you multiple reflections as some of the light bounces between the two panes. Now consider that the data is like a series of pulses of light. All those reflections will arrive at different times to a single receiver - the first bit being received, some reflections, second bit, more reflections from first and second bits... All those reflections make it harder to recover the original data.
