Wow! You give such great and detailed advice. Love it!
My garden spot is 46 ft by 90 ft. I realize region, soil, rain fall all make a big difference on how one does there garden. This is what works best for me. I do rows, (I know completely old fashion) The main reason is, it is so big, that I still need to till between the rows or paths. To much to hoe. Usually I can till it once in the spring, let the weeds sprout up and hit it again, plant and maybe have to till twice more.
When I do my rows, I plant two rows of all my vegetables about 12 inches apart and then leave a 36 inch path way on either side so I can till and hill them up as needed, depending on the vegetable. Some items that take up less room, like onions I plant more in that 12" spacing.
Another huge reason I do rows are the length of the garden and all the reasons listed by the above people about watering with a sprinkler. Sprinklers are a pain in a large garden, you have to remember to move them and we have lots of wind. So I use soaker hose. I like the canvas kind, easy to roll up and mine have lasted 5 years so far and no problems. https://www.frontgate.com/flat-weeper-2f ... redirect=y
The hose is easiest to use if you can stretch it out down the middle of my two rows and forgotten. I usually water once, maybe twice a week and all I have to do is turn on the faucet because each row has it's own soaker hose and is connected with spliters. So all eight rows ( actually 16) are watered at once. Leave for a few hours, and then turn off.
I have poultry netting for a fence so I try to plant vineing items next to it.
I too, would of tilled the topsoil into the garden, the grass would break up. Then I would of put the plastic down for a while and tilled again.
Good luck, hope it goes well for you.