Your closet is only 2 feet or so deep, so everything is going to have to be in rows. you got a ten foot stretch to work with, so maybe running two cool tubes in series with a carbon filter and fan would be ideal.
I'd probably still use a tent for good measure. Although it's hard finding 2 foot tents. Might want to build it yourself. Save you a bit of money, and the time spent researching will only make your skills stronger. I noticed some good DIY threads on here. There is one for making your own tent that looks legit.
For a closet, it's always safe to use a little carbon filtration. Don't need to get the biggest one for it to work either. Just gotta make sure you have a good enough fan for it.
the closet is a tent by itself, i dont see the need to place a tent inside it, just paint it flat white. 2 600w would be right for this room size with a cooltube, might want to place it on a shelf thats like 2ft high to make it easy to work with