No one who lives in either place would consider it a distinction without a difference. Ireland abolished slavey in 1171, although, like the English, they were involved in the Atlantic slave trade.
It’s not surprising I didn’t get the reference: there was no slavery on the Ulster plantation. That was about Protestant colonisation. The local Gaelic Catholics were displaced by Scottish and English colonists, not enslaved.
Plantation implies slavery in the US, but not everywhere.
Sure, why not? Again, a distinction without much of a difference when arguing what has and hasn’t been legal in England (proper, since most of North America WAS England/GB for 150 years) for 900 years. Sharecropping and multiple acts of genocide look pretty similar.