I do agree that some of them may be uploads.

I'm inclined more towards the creative robots being formerly human. The ones that seem to be able to have independent thoughts and plan things, like the Outsiders who plan to escape the city. Or in your example, the creative painters.

I don't think the musician robot for example is a former human. They don't do creative work, they can only do copying from the music sheets and have played the same things for thousands of years.