I can't answer the first part of your question, as its well beyond my period of expertise. But I can say for the second part of your question that you're conflating peasantry with serfdom, which I think might be the main source of your confusion on this matter. Peasantry and serfdom are not synonymous.

Serf is a legal category, though one which is quite difficult to define exactly given that the nature of serf land tenure, the rights, obligations and legal restrictions on serfs etc have varied a lot over time and place (being a serf in 11th century France meant something quite different to being a serf in 13th century England, which in turn meant something quite different to being a serf in 18th century Prussia and Russia). Whether serfdom is to be considered distinct from slavery (the position I take) or a form of slavery (its definitely not chattel slavery, like in the American South pre-1865, but its not a million miles away from debt slavery) is debatable, but kind of irrelevant to our purposes.

Peasant, on the other hand, is a socioeconomic category. There are a lot of different definitions of what makes a farmer a peasant/ a rural society a peasant society, and some anthropologists would argue that there's an important cultural dimension to it - see "The Origins of English Individualism" by Alan McFarlane for a discussion of the anthropological literature on peasants. I personally go with the definition offered by the medieval economic historian Chris Dyer, which is that a peasant is a small rural proprietor and cultivator who works on their own land primarily for their own subsistence. Peasants might regularly go to markets to sell their own produce and buy manufactured goods, as was common in most of Medieval Western Europe and China (see Chris Wickham, "Jiangnan Style", in "History after Hobsbawm: Writing History for the 21st century"), and they might do seasonal wage labour. But what crucially distinguishes a peasant from a farm labourer, on the one hand, and a capitalist farmer (the yeomen of late medieval and early modern England or the kulaks of pre-Stalinist Russia kind of hover between the two) is that unlike the former the peasant can still adequately provide for themselves from the land they own, they can do wage labour to make extra cash but don't depend on it for a living, and unlike the latter they farm primarily for their own subsistence rather than as a profit-making enterprise. The peasants of 19th and early 20th century France and Italy were peasants like the ones I have described, but they weren't serfs - the August Decrees of 1789 did indeed abolish serfdom in France and were indeed extended to the rest of Western Europe by Napoleon. I'm sorry that this didn't really answer your question, I just felt that there was some confusion that needed clearing up. I can however recommend that you read Eugen Weber's "Peasants into Frenchmen: the Modernisation of Rural France 1870 - 1914" (1977), as its the classic case for France still remaining "economically backward" until the final quarter of the 19th century, and has attracted a lot of scholarly debate and criticism since.