Billboard size is too big and i cant change for Landscape splines

Billboard size is too big and i cant change for Landscape splines ?!
And there is no settings about it .

There’s an option to change billboard scale. To edit splines just right click on them where you want to place a spline point.

There is no rendering options .
Just have 3 options ;
+Landscape Spline
+Landscape Deformation
and Mesh