For a 3'x3' area, 300 watts of COBs will generate PPFD values of around 900 µmol/m²s and the 400 watt COB lights will bump that up to around 1050-1100 µmol/m²s.
For a 4'x4' area, 600 watts will produce PPFD values of around 950 µmol/m²s.
For veg, you need roughly 1/2 the wattage as flowering, so you can either half the wattage or double the coverage area to produce PPFD values of around 400-500 µmol/m²s, suitable for veg, but low for flowering.