The potato farms I worked at in Maine sorted out all the small potatoes for seed and the larger ones for food. They sold both. So I eat large potatoes and replant small ones. The size and number of potatoes resulting seems more dependent on consistency of moisture in the soil though larger seed makes larger plants at the start.
Back to my lasagna planning, the lost little ones that came up in the greenhouse in February are close to harvest, some were pea size. The lasagna is a layer of compost to hold water and feed, layer of sand to protect the skin of potatoes from scab, layer of seed, layer of sand, layer of mulch.