I've noticed on 2 recent higher end restorations that the stripe wasn't applied correctly. They drew a straight line across the car, from side to side.
Man, I felt bad because they probably spent a lot of money to have someone who was an 'expert' do the restoration. I always wonder if I want to be the guy who says "your stripe is wrong".
On original cars I have seen all manners of finish at the ends (by the bumper). In some cases the stripe was taped off neatly, and in other cases it ended with an indistinct fog-out.
The stripe paint was applied first and then taped off and the main body color was applied afterwards, if you want to do it the way the factory did it.