Myers v. United States, written by Justice Taft in 1926: https://supreme.justia.com/cases/federal/us/272/52/

It contains an exhaustive historical analysis explaining why the President has unrestricted power to remove executive officers.

The “unprincipled” decisions were the ones like Humphrey’s Executor that sought to find ways to implement the 20th century concept of an “expert administrative state.” That’s not the government that was created in our constitution.