Can anyone explain what “Optimal Draw” does in 2.4 subsurf modifer? It doesn’t do what the old Optimal button did and I can’t find a way to get the old “fitted” wireframe which was handy for subtle modifications.
Here’s a pic that should solve your problem.
DwarvenFury
Excellent. I never even saw that button appear
One down, a few thousand questions left to go 
I can’t figure out what optimal draw does. I am also using 2.4. whether I have those two buttons in the picture clicked or not, optimal draw does nothing. Those two buttons from the picture do something but optimal draw does nothing, or so it seems.
from the release notes:
Now, the optimal draw button removes the extra wireframe lines which display as a result of having additional geometry. This button is especially useful to clarify and speed up the display of densely subdivided meshes.
GreyBeard