This is purely personal opinion and I have no facts whatsoever to back it up, but increasing
available airflow to the front grill won't help much if the air can't get out of the engine compartment. In my opinion, the most significant restriction is getting the air
out of the engine compartment. If the air pressure in the engine compartment is high, no amount of air flow at the grill will help.
I haven't had any engine overheating issues (at least that I know of), even while towing 7000lbs up very significant grades. I do have a larger aftermarket exhaust that probably helps a bit in this regard. The exhaust was installed by the previous owner, so I don't have any direct comparisons.
BTW, I have three large Hella lights mounted on the top of my bumper, directly in the path of the air flow.
Herb