My experience, watering with the Blumat Tropf system, is that roots grow towards wherever the water is at. Look at videos of grows using the system and you'll find "root mounds" 2-4 centimeters high. Of course I might be completely wrong about all of this.
Experimenting is fun-- I'm very curious to see how the experiment with 4000K@80CRI/3000@80/3000@90 will develop! (Right now, from what I understand, it looks like the experiment confirms common knowledge: "colder" light for veg for tighter nodes, and the the peppers seem to love 3K@90CRI)