Airflow Question about Growbox

Hello All,
I am designing a growbox to stick in my closet and i have a quick question. I will be using 2 41gallon rubbermaid storage tubs stacked ontop of eachother and painted to be lightproof for my cab. The question I have is about airflow: intake and outtake.
I want to us this DIY carbon filter i found on the site, courtesy of Wolman Zen:
https://www.rollitup.org/do-yourself/101248-best-diy-ez-walmart-carbon.html
and I want to attach it to my outtake vents.
This will reduce airflow considerable correct?
I was thinking 2 intake, 2 outtake computer fans to the cab. I dont know how big i should get to have enough airtake tho. Any ideas on the cubic feet of airflow needed?

Thanks

You are on the right track. I would say get a large computer fan and I mean more watts. the more watts a fan has the more power it will produce.

You don't need intake fans, only exahust. Use passive intake and active exahust, suck through your carbon filter (inside the box) and out.

Okay. Thanks. I never understood how to set up a passive intake tho. I can't just cut a hole lol.

Would 4inch fans be big enough?