The stores usually stay open for about another hour after the park closes. The lines for rides close when the park closes, if you're in line for something & you realize the park has closed, they'll let you ride.
I believe the express monorail runs for an hour after mk closes & resort runs for 2 hours, unless epcot is still open, but I'm not sure if they still stop at mk then.
They don't want you running all over the park taking pictures for a long time after the park has closed, but they won't kick you out right when the park closes either