Been using a pressure washer for many years, but do not expect it to clean on its own. Get one that will mix a cleaning agent with the water and use a brush to scrub with and the higher pressure nozzle setting to rinse with.
Many people are fraid to use a power or pressure washer but they can be safely used. Stay with one that is 2000 PSI or less as suggested.
If damage is being done it is the fault of the operator not the power washer.