High wing fighter? Eeer... did you ever heard of the Harrier? the Jaguar? the Tornado, the... in fact, now that I´m thinking... did you ever heard of any low-wing fighter? Most are high or mid-wing, hihihi. (Before any flak comes: yes, I know, the Bf-109, Spitfire, Phantom, A-4...
)
Now, trainers... Not much difference. Some tricks to go from one to another, some harder boarding in the Pipers... but that´s it.