Thats way too many plants for 400 watts even in an SOG setup.
At max you want to do 40 plants under each 1000w SOG setup. Realistically you should be flowering something in the neighborhood of 15-17 plants max per 400w light. Even really tiny plants like seedlings will veg up a bit during fruiting so take that into consideration. More plants doesn't necessarily mean higher yields. In fact too many plants will lower your yields since you not maximizing light usage.
Also the best way to do an SOG setup is with clones. It's a lot easier to do a continuous grow op off of clones that you know have the same nutrient and light needs with nearly identical growth characteristics. With clones it's easier to maintain an even canopy (since they generally all grow under the same rates). With seedlings your going to have to remove the runts that are just taking up space.
Growing off of seeds leads to some mixed up results. Some seeds will yield amazing plants but a vast majority usually are just average or runts. Also it's super expensive to continuously be growing with seeds (I'm assuming your not using bag seed). Clones literally cost pennies to make.
I'd also do a hydro grow vs. soil. It's just a lot easier to deal with if you know what you're doing and are on top of your shit. I will say soil at least has a larger tolerance to user error.