On the aircrafts systems & engines papers you are asked questions about generic jet engines, turbo prop engines and piston engines.
I remember getting a performance book with figures in, probably downloadable from caa.co.uk.
As I recall the questions were sort of based on a 737, something along the lines of a dash-8 and a piper arrow. It never actually said this, but if you look at the figures, weights etc that's basically what they were asking about.
So, sorry to say you need to learn all about the various types of hydraulics and electrical systems even if you are never going to fly aircraft with them. Remember at PPL learning about different types of flap, even though you may never see a slotted fowler in your flying days.