Your fans would exhaust more air if they were in a shroud which would not allow some portion of the air moved, to do a quick U turn and go through the fan again.
I've emplyed a 160CFM 230MM 12v computer fan as a stick and brick bathroom fan that could not use the traditional bathroom fans. Mounted in a acrylic tight fitting shroud in an upper window exhausting. Close the door and place a round pencil in front of it the 1/2 gap under the door, and it rolls across the room from the air flow from the fan on the other side of the bathroom. Without a shroud, fan just leaned against the screen, the pencil stays put with little discernable airflow coming under the door.
120Mm fans are numerous. I like the Silverstone fm181, 180Mm fan, as it comes with a potentiometer for speed control. At full speed it draws 0.28 amps and moves 160CFM and is still quiet. At lowest speed it is ~60CFM and practically silent, and 0.09 amps
Noctua makes extremely well designed computer fans.
The 200 MM NF A20 consumes 0.08 amps at 12vDC, and moves 86CFM for 18DB
More airflow than your 2 fans for 1/5 the electrical comsumption and likely half the noise, or less.
NOctua also has industrial fans, and some of these are IP 67( others are IP52) ratings, which should be better for cooking under. I have cooked under a silverstone fm121 for going on 8 years so apparently the grease and cooking fumes are not really a worry.
Noctua has their own PWM speed controller that can control multiple fans' speed
The 3000 rpm Industrial Noctua NF-f12 9120mm) draws only 0.3 amps and moves 110CFM and has a very high static pressure rating, and can easily be tamed to tolerable noise levels with their speed controller.
I employ two of them as intake fans, along with the silverstone fm181. Al three of them on max speed draw less than an amp and if they had no airflow restrictions in front of or behind the impeller, would move nearly 385CFM.
