I don't have a pressure washer but use a Dramm nozzle. I get enough pressure for my house and deck. You can do quite a bit of damage with a pressure washer. I learned about potential damage from our painter. He hand washes to prevent damage.

For my really grungy deck, I sprayed it, then put on some deck wash and let it repose a few minutes. I used a deck scrubber brush to loosen the dirt and sprayed off the algae and dirt residue
Would it have been easier with a pressure washer- probably but the 4 years of dirt would have been hard to remove with pressure alone without damage.

I have also used a pressure garden sprayer tank when a hose is not a good idea. A few years ago, we had a series of snow, rain and ice storms leading to giant ice dams on the roof. I put warm water in the tank and streamed water at the foot high dams until I had openings about every 2 feet along our south roof. It saved the day.

Bought a roof rake in Soo Canada last year so I am prepared.