Is there a way to display part range overlay without hovering a mouse over it?
Depends on the part, but you can use 'v' to toggle weapon range view (which comes with other features, too, and is the same thing as clicking on the little 'v' button under the Volley window). And for ranged utilities you can usually toggle them off and on again to have an animation that shows their range (since toggling is a free action).