Glad your enjoying the purchase [emoji3]
Pressure washing, just avoid obvious things like pointing Lance directly into it, (sounds daft I know but I watched a car wash chap do it to mine)
he ended up bending the intercooler fins [emoji35]
I usually wash the bonnet from the wind Screen down, and aim the lance towards the front end, that way I can give it a quick blow over and the water isn't directly going towards the scoop,
if your concerned you could always put a small towel over the intercooler and shut bonnet that should catch any stray water
Luggage covers are like rocking horse !Removed!, they surface on the bay occasionally but are daft money, you could try breakers, grade a subaru are usually pretty good, may be worth finding out if they are the same size as the impreza hatch,
As for roof cleaners ut's a pain as I tried once and got soaked, resorted to taking it to an auto valeting place where they had a wet vac, if you replay want a go at it yourself, autoglym do a foam shampoo spray which is a bit easier to work with than the normal cleaning agents