I use to work hard at planting things too close squeezing a lot into a small 20'x40' garden. I learned from experience my tomatoes get Sun burn in hot 100 degrees weather so I planted my tomato plants, 2 ft apart in rows 2 ft apart, the plants shaded each other and NO sun burn problems. I use to plant corn in a 10'x10' square, 11 rows, 1 ft row spacing, 21 seeds per row, pollination was excellent for such a small compact corn crop.
Now I have a 35'x60' garden and don't plant close like I once did expect for greens I plants in February. I planted 1000 Napa seeds in a 3' square LOL it came up like a crop of lettuce now it is all going to seed. I planted 6 kinds of lettuce the same way 3'x3' it is all too close. I planted Swiss chard over and over 3 times it never came up until a few weeks ago now it is all coming up all in the same spot. I threw 500 bean seeds in the garden all in 1 spot now it is all coming up, this actually works very well I have done this before. My tomato plants are under a shade tree this year doing extremely well, rows 3' apart, plant spacing 3' apart, 18 plants. My corn crop is 15'x15' square this year, 3' row spacing, 5 rows, 31 seeds per row.