Try it first without the filter (less drag) and see what you think...you might be surprised! I'm really not qualified though to answer about carbon filters etc. as never used/owned one.
That is the best benefit to passive exhaust into attic....most of the smell will go into the attic. Most of the time it will dissipate outdoors with little to no smell (as hot air rises). But when you have to worry is that last three weeks before amber trichs appear and if a low pressure system arrives (especially early morning and night) you can definitely give your neighbors a whiff but if any windy (and usually is when a storm about to hit) then pretty hard to locate where smell is coming from. And that's only like three weeks (one and a half really bad smell) every two months shouldn't alert anyone.
Also, remember lower temps...less smell.....higher temps more smell!
edit: main thing to remember when growing in a small space is air movement (specifically fresh air) as plants will use up air quickly in small space.
My last house I took duct work from the spare bedroom I didn't use and dropped it right down into closet so had both heat in winter and air conditioning in summer and had passive exhaust also at other end of closet from incoming air duct.
Just take a razor cutter and score the drywall (through the paper) and keep scoring around circle (cutting into the chalk) and then draw lines from circle edge to center and hit lightly with hammer.
Too plug hole can cram newspapers etc. or/and use mesh drywall tape and just layer the drywall in and will crack and shrink and go over again next day. If you can grow pot you can watch a u-tube on how to fix a hole in ceiling.