Advice for cob diy?

I dont know much about it but thanks to a few ppl here Im thinking im going to pull the trigger on a cob diy to the sum of 400ish watts??

couple questions tho.

-for my 2x4x5 tent is 400 watts enough to grow 2 nice yielding plants?
-do i need a driver per cob?
-should i have many lower watt cobs or fewer higher watt cobs?

Thanks.