How many photos in dwc or autopot/coco in 4×4 different strains

you could probably do up to 16-20 in a sea of green (short vege). If you have limited vertical space, this would virtually eliminate it for any typical 4x4 tent height. the more plants you do, the shorter the vege period you need to fill the area. So, that saves a bit of time/money. Probably a bit more effort with extra pots+watering each, extra transplants from seedligns etc etc. So, it's not all gravy. you could also do 1 plant, if you wanted. Might take 8-10 weeks of vege, but you can get there. 100% personal preference. If they all pull from the same reservoir, you better have a formula that works for 99% of plants. Don't assume the first product you buy has those types of results, because most marijuana branded fertilizer sucks a big fat dick, lol. As far as yield, as long as you fill the space and give the same DLI, you'll get the same yield, all other things remaining teh same. Genetics obvioulsy are a factor above and beyond that.

anywhere between 1 and 4, depends how your train the plant or plants. Make a plan and stick with it. I'd prob do 4 smaller ones. but you can easily fill it out with 2 or 1.

Good rule of thumb, plant won't grow bigger than pot supports. Big pots big plants, small pots small plants.

Easily get big plants with that 700w, id do 4. With at least 7 gallon. Smaller pots require more attention in that the medium drys faster. Not a great deal but once she gets bigger/thirsty she may require more than one session per 24 hours. My job often limits how often I can spend time with plants in any 24 hour period. If your doing autos or plan on flipping fast do 4-8 if legal to do so.

Depending on how long you want to be in vegetative state. You could go with one and let her fill out the space and she will harvest as much as 8 tiny plants. For some its a question of the electricity bill (veg means 18 hours of light) for others its determined by legislations saying how many plants they’re allowed to grow and some will prefer the product of a bigger more mature plant while on the other hand there are people who are more comfortable growing small plants. Genetics could also play a part in this decision but if you don’t know what you got and going from seed anyway you’ll never know how they will turn out. Even if you would know your seeds, a „strain“ or variety (genotype) has several phenotypes wich are all different, and breeders only give info about one. In the end its prefference. What i would be personally doing with 1,20m x 1,20m is 2 plants, since were only allowed to go with 3 in Germany. 4 plants would be more efficient though. If you start with hydro there is a chance that things go wrong in the beginning of the learning process so having more plants could turn out to be a smart when shit happens