stealth closet grow. need advice!

doing a small closet grow, personal, no more than 2 mature plants at a time.

The closet is fairly small, about 5.5 feet tall, 2 feet wide and 4 feet long.

I do not need the entire closest, and basically was wondering if it would be better to build a box to put inside the closet, and run my exhaust out of that, or just turn the entire closet into a greenhouse environment.

closet is in the attic of the house, there is a crawlspace that isnt insulated, so there is fresh air i can pull into the room through the wall. which hopefully will be able to keep it cool enough and a good supply of new air.

If i go with the box i would prob make a frame out of 2x4s and cover it with that white/black plastic. as long as it is airtight i can attach the carbon filter to the exhaust. I also wouldnt have to worry about light leaking from the closet door because the box will block all light. Im not sure where i would put the exhaust though. the intake will go through the wall into the box, would it be okay to put the exhaust in the same wall? i dont want the hot exhaust air to get mixed with the cool intake air. also wat about passive intakes? ive always used intake fans before but wondered if i should look into it. basically 1fan for intake 1 fan for exhaust OR 2 for exhaust with a passive intake.

been shooting ideas around for awhile in my head but thought i could get some help on the brainstorming. this is only my 3rd grow. i know a little but ive never done a closet grow like this with the closet itself being so small.

any comments would be appreciated! no pics...mostly because i dont really have anything to take picutres of at this point

You just have to remember to put the passive intakes low to the bottom of the box and the exhaust near the top.