NFTG#4 is a coco based soil mix. It has ewc, humus, and other amendments that hold a lot more water than the standard coco/perlite grows you see on here.
I use their #7 expanded coco because I'm a local and their prices are nearly the same as buying wholesale bricks. I have added perlite and ran it pure and had good results both ways.
If you use their nutrient line and water like its soil the #4 grows great. My associate swears by it and gets tip-top product. He just spends $200 a grow on nutrients and soil. I spend $30 on nutes, and reuse coco.
Coco is so much cheaper and quite forgiving. Forget soil unless you are going no till.