A sea of green is only considered a SOG when you do not have to top your plants to fill in the horizontal space. If you are having to use any sort of plant training then you are technically not operating a sea of green.
9 plants in a 4x4 is what i consider the bottom end of technically SOG. And the top end being 36, any more and the gains are very minimal and possibly decline due to added complexity. 25 is a good medium ground.
Here are the plants per square foot for 4x4
1 plant per 1.8 SF = 9 plants
1 plant per 1 SF = 16 plants
1 plant per 0.64 SF = 25 plants
1 plant per 0.44 SF = 36 plants
Here are the plants per square foot for 2x2
1 plant per 1 SF = 4 plants
1 plant per 0.44 SF = 9 plants
The reason there are only two choices for 2x2, is because of symmetry. You ideally want to have a uniform ratio that matches the room that it is grown in. Which only allows 4 and 9 plant configurations as they fit between the 1.8 - 0.44 SF range.
Hope that makes sense ^.^
4 plants should be plenty for a 2x2 space if you are planning to grow them out all the way in that space. Thats like having 16 plants in a 4x4. If you are however using the 2x2 just for vegging and moving those plants elsewhere later on, then you can do 9 plants. Saying that you could possibly get away with 9 plants for a full grow in 2x2, but it would be tight ^.^
Any further questions feel free to ask.
