Problem

Display Visible Edges is greyed out when display Style is set to Filled Hidden Line

(You can actually set this on by changing Display to Shaded. Tick on Display Visible Edges, set your overrides, then set the Display back to Filled Hidden Line. The display visible edges is now set.)

Solution

This setting makes no difference for (Filled) Hidden Line

From the help files:

*Display Visible Edges* (Shaded render mode only) If on, visible edges are displayed in views to which the selected display style is applied.

*Override (Edge) Color* (Shaded render mode with Display Visible Edges on, or Filled Hidden Line
render mode) If on, controls the color in which visible edges are displayed in views to which the selected display style is applied. This true color overrides the edges' element or ByLevel color. Clicking the adjacent color button opens the drop-down Modify Color dialog for setting the Override Edge Color.

*(Edge) Weight* (Shaded render mode with Display Visible Edges on, or Filled Hidden Line render mode) Sets the line weight with which visible edges are displayed in views to which the selected display style is applied.

*Hidden Edge Style*(Hidden Line render mode, Filled Hidden Line render mode, or Shaded render mode with Display Visible Edges on) If on, sets the line style with which hidden edges are displayed in views to which the selected display style is applied.