No problem removing the stripes. I'm not sure where you're located but if it's relatively hot, you shouldn't have any problems just pulling them off once the car heats up from the sun. You can also use a hair dryer, not heat gun, to remove them.
The stripes by the rear spoiler does not go under the stripes so you don't have to remove the spoiler. As you said, pull them at an angle. Good luck!