I have an update. Since I sealed those gaps off and put those plastic plates on the sides of the radiator against the bumper cover, I noticed that bugs and other debris now seem to get forced deeper into the fins of the AC condenser, which would seem to indicate that the air speed through the radiators has increased. In stock form, bugs would barely get stuck to the condenser's fins and would usually fall off from barely touching it or rinsing it off with a garden hose. However, since I performed these modifications, bugs now seem to get forced between the fins much deeper and needs to be picked out rather than just brushed or rinsed off. Not scientific, but it does indicate that my modifications seem to have increased airflow through the AC condenser and the radiator.
The other thing I noticed is that the car seems to feel more stable at higher speeds now. It always drove well at high speeds, but it just feels a little bit more stable and predictable at speeds of above around 70 MPH than it did before. I don't know enough about aerodynamics to why this is, but I'll take it
