The definition of low light to most people new to the hobby is whatever light came with their aquarium, and then maybe bumping that up to between 1 and 2 watts of flourescent light per gallon of water. I don't think half the plants on your list would grow in those conditions, and even if they do survive, what kind of condition are they in?
Name a single species of any plant that cannot be grown to a high level at 1.5-2w/gal of PC/T8T5 lighting?
Low tech will include CO2 or not? If so, then it's not the light, it's the CO2.
If Excel is included, then there's little issue.
The light level in this tank is the same as it is it is in the other:
Light was measured using a PAR meter at various points in the tank.
What does well in that tank, is independent of light for the other.......
Adding CO2/Excel will certainly extend and promote plant health/growth at lower intensities of light, this is well documented and Tropica has a good article on that subject.
You cannot get away from the holistic aspects of growth, light, CO2 and nutrients, not just one of these parameters.
Non limiting CO2/nutrients allow less light to be used and extends the lower range of lighting.
That's right smack in the middle of the range you suggest is unacceptable for plant growth for the specific plants you mentioned, HC, Gloss, Stem plants etc.
Maybe for non CO2/Excel, but not in the broad sense.
But if you add CO2/Excel, then it's not independent of lighting is it then?
So it's either both light and CO2, or not lighting alone. Something else is limiting, hampering growth etc, not light.
Otherwise, the above examples cannot be possible, and yet......they are.
Several hundred folks in the Bay have seen those same tanks.........
I have never been particularly keen on calling aquatic plants low light vs high light. They all do pretty well at some rather low light levels and the low light plants grow pretty fast at higher levels of light as well.