Vents in the outer soffits will create airflow which will PUSH out all of the warm air (settling in the opened space up there) until the temperature is even. Since the soffits under the eaves are LOWER than the gable, warm air is going to be pushed out the gable while cooler air enters via the soffits (below). Hence warm air rises; cooler air sinks.
Good luck! And keep your eye on your post for other 'thoughts'.