Also the "end" of the cars depends on which direction the train is travelling (to Tokyo or from Tokyo, etc). It can be row 1 or row 12/15 (or how many rows of seat the car has), so if you are going to reserve the seat(s) at the end of car, just be sure that the last row.

My friend and I took the Hokuriku Shinkansen one time (green car) to Kanazawa and the space at the last row was enough to fit two 25"/28" full size luggages on each side.