Does everybody have at least a little plaque in their arteries?
No not necessarily .
The innermost layer of blood vessel is called endothelium.
The endothelium prevents accumulation of plaque on its surface. Any injury or thrombus on the endothelium resists blood flow. Blood platelets adhere at place of thrombus. This makes the thing worst and allows formation of plaque. Body is having a intrinsic method of plaque removal.