Velocity Stacks and Scoops ???
The benefit of the velocity stack is to both guide and smooth the airflow into the carb - less turbulence than having to climb up and over the top flange of carb. Check out most all engine dyno comparisons and you'll see a velocity stack used.
Of course you'll get a better result from the scoop if it's sealed to the carb since there's noplace else for the air to go except down the carb throat. The cooler outside air is also better since it's denser than hot underhood air. Doesn't matter where the cool outside air is coming from as long as it's coming from a high-pressure area like from a hoodscoop, front of car (radiator/headlight area - think Ford Thunderbolts), under the bumper with hoses (think Olds W-30 442), or base of windshield (think '67 Camaro Z28 or NASCAR airboxes).
Remember, you need a minimum of 30 sq. inches of scoop opening to get full benefit of an open scoop.