Well, I can take a stab at the crops. You'd expect to see Fagopyrum tataricum, a type of buckwheat, which was domesticated in the region and does well in the early winters found in the region. Brassica rapa var. Oleifera (oilseed rape) has a purpilish form found in the region, and the shoots are often eaten beyond being used as a seed oil. Vigna umbellata (ricebean) was possibly domesticated in the region, and is well known as a cultivation crop there. Perilla frutescens var purpurascens (lamiaceae) is a wasteland plant that is also cultivated in the region. Colocasias (taro), Setaria italica (foxtail millet), Avena (both chinensis and sativa), likely any number of beans (genus vigna and canavalla), tubers (particularly Dioscorea genuses), Morus australis (a type of mulberry) and its cousin M. nigra, would have been used for fruit, Juglans (iron walnut trees), Corylus (a small tree with edible nuts), Cerasus humilis (a type of shrub/bush cherry) and C. japonica (bush cherry)...

The list is rather huge. I recommend checking out Plants of China: A Companion to the Flora of China, edited by De-Yuan Hong and Stephen Blackmore, from which I culled most of this very quickly. There were a huge number of cultivars historically in the region, and you would have seen a lot of variation from micro-region to microregion, just as in Europe.