Follow what I did in the diagram(box2). There will be too much air restriction and heat will built up too much otherwise. Growing one plant in flowering will yield better than two. I would clone the first plant before you flower and then grow the clone, once the first plant is harvested, clone the clone, flower the first clone, grow the second, repeat. You can do a tradition a mom/clone setup also but this way is easier once you can clone perfectly every time. I would take 4 clones each time just in case while you learn to clone with 100% success and either save the others for later harvests or destroy them. Use CFLS for the clones or even better PL-Ls. I don't think a T5 fixture will fit in your space, if you find one that does, use that. You want something as close to 6500K as possible for the clones. A 250w may be a big much for that space, but only because of heat. A 150w will cover the same space and give off less heat but will not give as good of results. Worst case is you find out the 250w is too hot and you end up buying a 150w and then you have a 250w for when you can upgrade. If you can spend the money n a quality LED panel, that is an option but that will cost 4x as much but could give better yields if you get a good panel. Personally I wouldn't get the LED panel, but it is an option.The main flowering space is just fine for one nice plant but a tad small for two, especially for a scrog. Doing a scrog on a DWC in a confined space can be troublesome when you need to clean the res out which should be done once a month. You also might have problems checking your PH/nutes/etc. every day, which you will need to while you learn how to do hydro. Soil would be easier but DWC is totally doable. You may want to just tie down instead of scrog which will give you the same results but will be far more flexible when you need to access the res.
You will want a 12"x6" scrubber with a 4" dayton/axial fan to handle air and smell. A 6" fan would be better just in case it gets too hot, put a fan controller on it to turn down the noise if needed. A 120mm PC fan should be used for the clone chamber exhaust, maybe two if the heat is too high in the clone chamber. You may need to move the scrubber to fit it in there right but that size should be more than adequate for the cab.
