The majority of ex saves became share croppers on the exact same plantations ...
It seems that both points are true and together they point to a larger difference between North and South at the root of the slavery issue.
Agricultural economies do not have the cash needed for wage labor. They could produce on average two crops per year, giving them two payouts per year. How could planters keep a ready store of cash on hand for wages? Banking was relatively primitive.
German homesteads in the North were successful--but they never produced on the same export driven scale as the planters. I doubt they could have.
The North never seriously dealt with this problem: provisioning the labor needed to maintain agricultural production-- at least to my knowledge.
Nor did north's invasion improve these circumstances--as evidenced by the share-cropping system that replaced slavery.
Lincoln was a capitalist and did propose solutions in this direction(rejected by both sides) suggesting some insight. I can't say how comprehensive his understanding was, or if he had sufficient power to do anything, but he gets some credit.
FWIW-I'm no historian and others here know more. So, fire away.
The main difference is that farm labour needs in the north are much more variable by season than in the south. In the northern climate it makes no sense to feed & house slaves year-round when the growing season is only a few months; it is more economical to use paid labour for the growing season only. The typical pattern in Canada for unskilled labourers was to spend the summer working the fields, then spend the winter in logging camps (it’s easier to move lumber overland if the ground is frozen).