It’s difficult, in some ways, to document the social background of many of the settlers because they’re not people who kept large numbers of records in their family papers. But any work that has been done, particularly by Michael Percival Maxwell, suggests that many of the settlers below the level of the landlord, were very poor people.
The Scottish economy was in decline in the 1630s in particular. Very poor people from rural Scotland felt that Ireland offered them more prospects for improving their economic condition. But they came over to Ireland with very little: they came over from rural backgrounds where they were probably used to a pastoral form of farming. So when they came onto the Plantation lands, they had very few resources to exploit the land in any innovative way: they simply want to continue on the same pastoral form of agriculture that they had done in their own home areas back in Scotland. So they continue in some ways the same fairly low level of subsistence in Ireland as they had had in Scotland.
At the landlord level, James I encouraged many of his friends in the nobility in Scotland to invest, and to take on the responsibility of being undertakers in Ireland: but some of them did it very reluctantly - they remained absentee landlords. Some of them did it very enthusiastically, and the Scottish undertakers were far more successful in the development of their estates than the English undertakers.