The short answer is yes they help keep the cost of damage down. A couple of things though, like the catch and tumble the bike? Yes the point of contact is higher than the bike sliding on its side BUT that only counts if the bike is sliding backwards ( tank first) and if it's going away from the tires it's going to turn over anyway. The other is that the slider or bolt will actually damage the frame or engine mount, Yes and no, it depends on the manufacturer. I made my own for years sizing the bolt and sliders to give but protect. R&G are simply the best engineered sliders I have used. We have not had one damage an engine mount in five years. What that means is the bolts give and bend correctly, too stiff and the bike will give. That bending bolt has done some minor damage to bolt face on the frame but it is of no consequence.
Yes again to the package effect of sliders on all the high points, the more the better. We have had many bike go down and need only the sliders or a case cover to be ready to go again.