Cubic Feet Question and couple more q's

I am thinking about starting a small grow with some AutoFlower WW. I am looking at a 4x2x6 tent that has 40 Cubic Feet. I was wondering can I get 3-4 plants into it without struggling? I am thinking of a 250 or 400w HPS, or Possibly CFL's 1000w CFL total. Which would I benefit more from? I will have my tent set up outside so I am not going to worry too much about carbon filters. Will I still need intake and exhaust fans set up for bringing in fresh air and getting rid of the hot stale air? I have some nutrients not sure if I have enough so I wil be getting more not sure what kind yet. Any recommendations? I will be growing in soil probably 3 or 5 gal pots not sure, any suggestions? Did I miss anything important? Thanks!

You'd do best with a 400w hps. I have a 2x4x5 tent and use a 400w. I've grow up to 8 plants at one time in there, sog style. Currently I have 3 Trainwrecks going in 3 gal. fabric pots. The picture is about a week old. Unless your going to leave your tent wide open with a fan blowing at it, you'll still need an exaust fan to exchange the air. Even though your grow will be outside, you may still want a carbon filter. Nosey neighbors can be a the death of a garden.

Don't stress the nutes too much, just give them good, clean, we'll-drained soil. Grab some bat crap, maybe some molasses and some trace minerals, and call it good.
Totally agree with Raven on the lights. Just pick out a good light package for your venting needs, etc and you'll be golden
I hope it comes out well, and hopefully your outside RH doesn't get too out of hand