Yield and Space

Do you concur with this?

More or less.

Yup. If your space is too small and you have too much light its not good and if your space is too big with a small light its also not good. The authors explaining how light size and the space youre filling are proportionate. What part do you have a problem with?

Pretty much, but I'm not sure about how they have the plants arranged in those pics. I'd have those under the 400 in a 2x2 square instead of one row. Those lights look like thye'd project a more square-ish light pattern.

400 is 70cm x70 cm for me here perfect coverge for 4 medium plants.