The phaser beam would hit enemy cover and background props in dramatic showers of sparks, of course.

You know how it is. Storm Troopers always forget to switch the dial.

It depends on who they're shooting at.

In the first movie, they were extremely accurate except when shooting at Han, Luke and Laia.

Those three escaped the Death Star, and the tacker on the Millennium Falcon led the Empire directly to Yarvin 4.

The next appearance of the Stormtroopers had them be Flanderized to the point where literal rocks were their Achilles heel.