If your going to use PL-Ls for the veg, which is a great idea IMO. Then you can get a nice 2 light setup with reflectors from here http://www.ahsupply.com , bulbs aren't included but you can get some for cheap from 1000bulbs.com . Your space is tight but I think it can be done for sure, if the 150 watt hps is too hot you can always use PL-L or CFLs for flowering too, seen some great success with them.
Forgot to add this link to some of the best DIY stuff from this site, theres some good solutions for light tight ventilation along with tons of other great DIY projects that should help. https://www.icmag.com/ic/showthread.php?t=40637
Good to see your starting the construction of your cab, I've been working on my new cab this week, can't wait to finish it and get it going.
I think you could do 4 plants can just scrog them vertically but maybe starting with 2 is smarter so you can get the cab dialed in. You just using bagseed to start off?