In the ghoul settlement of Necropolis in New California, the glowing ones lived in the remains of Vault 12, and there was an animosity between them and the "normal" ghouls led by Set, who inhabited the ruins of the town. After Necropolis was overrun by the super mutants, the glowing ones who left the town lived much more harmoniously with the other ghouls (not to mention normal humans and super mutants).
They are former humans who absorbed enough radiation to the point that they are luminescent with it. Unlike their less fortunate counterparts in the Mojave Wasteland and the Capital Wasteland, the glowing ones in New California are rarely feral and usually completely sane.
These glowing ones are working in nuclear power plant in Gecko. The radiation doesn't have much effect on them. If the Chosen One fixes the reactor's radiation leak, the ghouls in the plant (not just the glowing ones), will comment on how the plant feels "chilly".