So in RQ, a “hide” is a unit of accounting and not really of area. It represents the amount of land sufficient to support a household or meet certain fiscal duties. The concept appears in a lot of different real world cultures:
The Ancient Greek kleros was not a fixed unit of measurement but a socio-economic concept referring to a plot of land allocated to a citizen, often sufficient to support a household or qualify for military service (e.g., as a hoplite).
In medieval Germany, the Hufe (or Hube) was a unit of land capable of sustaining a family or farmstead.
In the early Islamic Caliphates, the jiftlik (or jift) was a unit of land used for taxation, roughly defined as the amount of land a pair of oxen could plow in a season.
The zeugarion was a fiscal unit of land in the Byzantine Empire, defined as the amount of land a pair of oxen (zeugos) could cultivate.
So in RQ, the amount of land that constitutes a hide is going to vary based on local customs, soil fertility, and agricultural productivity. In Sartar and Pavis County it is typically somewhere around 4–15 hectares.
Now usually, a free household in Sartar with one hide of land will also have something around 2–5 cattle, 25–60 sheep, 3–5 pigs, and 10–20 chickens.
A peasant can be a free commoner – the word basically just refers to any rural farmer of “lower social class”. Although the word includes peon and serf, it also includes free farmers, small landholders, etc.
Part of the reason a lot of these sorts of words rarely work well in TTRPGs – we like precise definitions for games, and many medieval terms are very imprecise.