1 Rockwool...just works, is easy and cheap,..
2, I run 5,8 to 5.9 in a 19L DWC,
3, depend on what light you have i generally go wth 2.5 to 3ft ..
4, even un ph'd tap water is fine for up to 2-3 weeks into veg from seed,
5 i just put the rockwool and seed straight in the hydroclay filled...