18/6 is what I like others use 20/4 quite frequently, but really it’s preference.
As for making fem seeds with STS or CS , all the seeds I gave you are feminized, but you don’t need or want to really spary till week 2-3 or once they are thinking about flowering, my suggestion though is pick the best plants and reverse those, unless your using Reiko’s seeds as apart from his fam’s they are standards and you can make seeds the standard female male way.