I tried to do the same thing. I need this setting for users that still want to change the font size. So i disabled the group policy setting "Toggle Settings Display Control" and put the "Prohibit selection of visual style font size" back to not configured. Did a gpupdate /force, and rebooted my machine. Still the same greyed out settings. Then went to the registry, changed the NoDispCPL to 0. Logged off my VM and logged back in. Still the same issues. If i take another look at the registry key NoDispCPL it's back to 1.
What am i missing ?
I would be very grateful if somebody has an answer.