For sure man, that sounds like fun. I have been doing an experiment of my own for many years. When the switch to led, is was apparent there were differences , but I wasn't sure what it was. Spectrum and intensity both have an effect on the plant, but the spectrum actually seems to affect the genetics themselves. You have to have grown enough of the same strain to get the idea.
My last grow I went for it totally and grew the same, normally stable strain from DP called Auto Night queen and ended up making four different phenos from the four light spectrums I introduced.
I noticed this before in other strains, many times, but I have never had the gonads to fill up my space with only one strain and do the experiment to finally see if there was any validity to this theory.
As far a second the stretch goes, I have has no issue getting stretch out of the plants and huge yields, but the plants that stretch most are still getting that blue spectrum you get from cobs and QB 's, plus the IR and deep reds at the opposite end. The combo of these two together get better stretch than if I use only veg light on the led blurple I also have.
I have a blurple that runs 180 w from wall, a Chinese QB look a like( nice parts with two meanwell 150 w drivers) running at 200w from wall, a cob light with two 3000k Cree chips running 150w from wall, and two individual cobs, both running 3500k, one at 65 watts with plastic white reflector, one at 100w with glass reflector, both Cree 3590 chips and meanwell drivers. I will still add a 6500k or 6000k into the mix and an additional IR as well to really give me some spectrum flexibility, plus theee are many options to build QB set ups with complete control over spectrum or buy the special Lights to better control that. The investment was pretty large, so I went this way as a first step. My wife would kill me if I spent more money on lights right now to fit the entire room, so I am doing it this way for now.
Let's see what we can do. I was going to start a grow at the end of this month. Where are you at in the cycle?