Selucia may or may not be property but I lean to the not property view. There was a scene where Selucia was dressing Tuon and there were the usual da'covala there helping her but they never touched Tuon only Selucia did this. I took the way it was written to mean that property would never physically touch someone so high ranking at Tuon hence Selucia being freed.

One other thing to be clear on is that da'covala status is heredity but there seems to be several type of da'covala. The ones we have seen the most are the deathwatch guard and the servants who wear the transparent robes. There was also reference to a deathwatch guard officer being chosen as a child but I think that his father was a weaver or some such while still being property. There was even a reference, I think from Suroth's pov, about some property being put to work sweating on their backs or some such vague reference that seemed to suggest a form of prostitution.

I could be wrong here but my take on things goes as follows:

Criminal/Gross incompitence/rebel = da'covala who becomes either a menial servant or worse. The loss of status is the punishment but so is being kept in a very menial if not degrading role

Hereditary da'covala to include offspring of criminals = tested to see where their tallents lie as children and put into the appropriate carear training which can include being made deathwatch guard or perhaps a weaver or if they are very graceful, or pretty becoming a dancer or personal servant.

Both are property but within the same social class there is differences of status.

One think I have wondered was about the story of the drunk nobles who had themselves tatooed as a lark and when the empress found out about it became property in truth. If they had any children after the children would probably be born property but what if they had offspring before their fall from grace. Would they share in their parents new status. I suspect they would be okay as under the Seanchan rule a free person seems to have to do something or fail in some way themselves to be made property but I wonder what anyone else things.