I read this series of books in the 90s. One book focused on a dome that held a technological society that would put information in their heads using microchips. They were bald and unfit as information was the main part of this society. The society was also hierarchical and they had servants. There was some resistance and underground rebellion that the main character, a boy, ended up joining. The other book I read featured a dome where the societies had psychic abilities except the main protagonist,a girl who seemed not to have psychic abilities. They put her in a black room with no 'noise' and seems to 'hear' something from far away. She and some others set off to find this signal that turns out to be coming from the technological dome.
In Devil, the ruling class are considered more important the more knowledge chips they have plugged into their heads, causing the most learned to walk permanently stooped (hence the title).
All the other points you mention match; the boy is the protagonist of the first book and the girl is from the second.
The books were published in the 80s so the timeline is right. Devil is a great read for kids, too.