Fastest and cheapest would be 4 plants with little to no vege time. Just go 12/12 from seed, maybe 1 week of vege?
It's wise to have some space away from walls, so a slightly smaller than 2'x2' plant prolly takes anywhere from 4-6 weeks of vege to properly fill that tent with 1 plant - depends on grow method as well as genetics. *method being soilless/hydro vs soil.. whether you lst or top shouldn't impact this as long as it's done right.
1 less month of electricity is not a huge amount, but also 1 less month waiting for harvest.
plant 6-8 so you can kill any weak or retarded plants. Even if you go with 1 plant, plant 2-3.
There are qualitative reasons to go with 1 plant, but as far as cost and productivity, more plants is better. More plants also hedges bets against a turd genotype. when you do get one it's a smaller portion of canopy vs 100% of it.
symmetry helps.. symmetrical growth is easier to shape into a square than a rectangle. Trying to make a plant oblong can be the cause of needless excess vege time and extra pruning of wasted growth on the short dimension side. I'd stick to 1 or 4 plants. 9 would be too many in 2x2.
