My lights have their own dedicated fan. It pulls air from outside, through the light hoods, then it goes out the tent, through the fan and exhausts out of the house. No filter on that one, because everything is sealed. I think like your second diagram, except my fan is outside the tent on the other side of the lights (think your farthest red arrows in the last diagram). Separately, I have a second fan that is just for exchanging air in the tent. It pulls through the filter, then fan and out. Did I explain that right? It works good for me.
Is the lower left fan in the last diagram intake? If so, you shouldn't need a filter on that one, as negative pressure keeps the smell from escaping there. Heck, you probably don't even need an intake fan there...
So are you pushing air or pulling it?