i used to clean my R32 engine bay with Autoglym engine degreaser and a hose pipe. Just kept the engine running and let it warm up first, neve rhad any issues whatsoever. I tried the autogym plastic and engine spray but aerospace is so easy, basically once its cleaned spray it all over close the bonnet leaving it on. wake up and in the morning its all dried and shiny, Amazing stuff. I only really cleaned the engine bay once a year.
Best thing is just use open ended hose, not a pressure washer so the water isnt forced into places it shouldnt be.