Perhaps the Spanish Portugese approach was more in line with medieval europe, whereby I don't know all nuances of differences across Europe.
In the medieval Low Lands and the Holy Roman Empire (and I think also France, UK), all at that time the feudal system and Catholic area, there were several grades.
I am not exactly sure about which English words apply, because most of the time in English texts it is simply serf or peasant. And for my feel serf used as catch it all.
If you look at the basic rural set up, you have a lord (the small ones more a farmer with rights) that has in Dutch "lijfeigenen" and "horigen", and in my awkward Englis translate into "body-owned ones" and "belongers".
There is a huge difference between these two kinds of serfs. The "lijfeigene" more in the direction of a plantation slave, the "horige" more in the direction of a small peasant that rented his land (tax) and had duties to do for the lord.
Or more in Carolinguan law terms: two kinds of un-free: one bound to the land (the "horige or more fundamental a "laat") and one bound to the land & the lord (the "lijfeigene" or "full serf")
Both had a really huge range in what it actually was.
With the more slave like serf, the "lijfeigene" there were many variations as well, from more to less free.
But basically they had the right to own and accumulate money, the right to found their own family and the right not to be sold (no family separation !), unless sold together with the land they lived upon. In any other sense AFAIK they were like plantation slaves.
Perhaps the most simple way to show that for that small medieval peasant is the number of different words in use during the Holy Roman Empire in German language:
* you had the free peasants called: Bauer, Vollbauer or Hufe. They owned their land, but had to pay taxes, and had duties.
What I know about old medieval documents in NL is that these Hufe peasants, in Dutch "Hoevenaren", were named as witnesses in important transactions for nobility.
The rest was also bound to the property, the "earth" of the lord (they could not travel away).
* peasants with good holdings: Meier, Freisassen, Schulzen, Fester, Grundholde, Hintersassen, Hörigen, Hintersättler, Hintersässen, Hintersiedler, Beisassen,
* peasants with small holdings: Kossaten, Kleinhäusler and another couple of names.
* the landless "peasants" another list of names
Most of the rights these serfs and peasants had were a hybrid between property thinking of the lords and human-social considerations of the Catholic church. Going into many details like what happens when a "lijfeigene" marries a "horige" or a free farmer, what status do the children get, etc, etc. What price to pay the lord for status-equal and status-unequal marriages, etc, etc.
Perhaps for our USians and other English speaking people living in former UK colonies: medieval europe was a highly regulated society !
Not only these societal laws, but also for example the regulations on quality controlling the food bought in towns on town-markets ! The town council felt, was expected to, took, responsibility for the food health of its citizens for food bought at the town market (not on what their citizens bought or did outside that market).
The people that left Europe to the New World, the new colonies, left all those regulations behind them, and invented the wheel themselves with some remnants of the Old World.
Not only the farmer settlers... but also the wealthy adventurers, starting plantations. In principle they were unbound by rules of the past. More the libertarian type than the people staying in Europe.
I guess it made a difference, also for the slave approach, from which European country these adventurers came and how the nature of connection with the mother country was.