Questions about my grow room

Question from a fellow grower:

Planning to grow all compact\feminsed plants:

  1. Box: 24inchX21inchX46inch

  2. Mylar coated inside

  3. Galaxyhydro LED(3w)300w Greenhouse Indoor Hydroponic Grow Lighting 9 Band

  4. 14 Gallon Hydroponic Tube 15.9"l X 23.9"w X 12.2"h

  5. 28 inch Grow Height

  6. (2) 200mm Fans-Intake and Outtake Center of box

  7. 3inch Hydrofarm Net Cup (1 inch under water)

  8. Closet ambient temp is 80degree F

  9. Do I have to change water in hydro tube? If so, how often?

  10. Once I germinate seed- I can I place directly in 3inch hydrofarm
    net cups or do i have to use peet disk\soil or root wrap\soil?

Question: How many 3inch net cups over 16inch by 24inch(2.6square
ft) should I use? I was thinking 6 cups over 2.6 sq ft or 5 inch per
plant. Will 12inch deep be enough for roots

Plan B: If I need deeper root deep to 16inchs, i can go modify box and allow for about 28inch clearance from top of box.