2 questions...

first one, why wouldnt a greddy exhaust made for a 97 hatchback fit a 97 coupe. its just a cat back, i thought it would probably work but i was told differently...

second question... what kinda of engine swaps are out there for the 6th gens... are they the same as the 5th gen swaps? i wasnt really clear on this cause i never seem to find anything for a swap for a 6th gen or newer, but i think thats cause 4th gen and new are the same maybe?

Exhaust will not fit coup, hatch and 4 doors are different.

As for engine swaps there is a FAQ at the top of this forum you can read about it there.