Fences, patios, existing ornamental gardens will restrict the flow of the garden & how large it can be.
When placing veggie plants among your ornamental, consider the look of the entire plant
Some veggie plants are attractive and others, quite frankly, are not! They may start out looking great, but not so at the end of their cycle. Take that in consideration when placing veggies among ornamentals.
Rows vs. beds:
Rows are just sections measured out 3-4 ft. wide & any length. Usually you can just remove the grass & weeds, till deeply, 6-12 inches. Incorporate any amendments & fertilizer when tilling. Paths between rows should be 3-4 feet wide.
More highly recommended would be beds. You can make beds, sections made into any shape. Beds fit well into smaller established yards, just find pockets of space in the sun.