well let's say you go with plan A. u still need more powerheads for more flow, i dont think the return pump is enough flow
but anyways GL with which ever plan u choose
yea like Finding Emo said u can always add the sump/ fuge later since your using an overflow box, which is what im doing with my 20L, i going to turn my 10G tank into a sump/fuge, ill have it running as soon as my stuff from marine depot arrives