The settings for this are in Rhino Options > View > Display Modes > _[your display mode]_ > Objects > Surfaces.
For technical display modes, the setting is in ... > _[your display mode]_ > Objects > Lines.
The only thing that is lower than 1 would be 0 - turning the edges off.
Tangent edges/seams is a property of “regular” display modes and is not found in “technical” display modes.
-wim