the box is 4ft tall but then subtract the height of the grow tub and light, minus the height above the plants that light needs to be and you're working with more like 20" max. That maybe 20" space is the actual space you have to flower in. They will double their height in flower, keep that in mind. If you're growing trees then yeah a good veg helps but in micro cabs it will only cause lots of hassle pruning tons of stuff just to get it out of the way.
My last cab was only 30" tall, it was a royal pita keeping them from overrunning it, you'll see soon. If you choose to veg don't go more than a week after the roots hit the nutes or you'll be sorry trust me. Also starting at 12/12 will get you to the end faster, it's basically an autoflower with 50% less lighting time.
top the plants after the second leaf set, that will give you 4 tops each which is easily managed in a small space. You'll need to either screen them or stake them up somehow, I'd build a screen about a foot tall onto your res lid so you can lift it to change the water, or get a small fountain pump to pump it out.
A screen will keep the tops in one place and give you more room to work with between the light and canopy. Training will be your best friend here, you have to forget all that hippie dippy let her grow wild and free and recreate nature shit, in a tiny space you have to be like the ruthless corporate boss, cutting out the fat, making the hard choices, bending nature into submission and cramming it somewhere it does not want to be.
edit: Just noticed you got connoisseur, I haven't used it but from what others say its pretty stout, try lower doses til you get the hang of it. Their basic grow micro bloom set is what I use, just tread lightly and you should be fine.
