... Lets say I get the 300CFM one. Won't it fry the controller board if I just plug it in?
Because fans speed is controlled using a PWM signal, possibly but not certainly. With PWM control all power switching to set speed is done in the fan itself, the controller just supplies a low level control signal to the fan.
The concern is the size of the circuit board traces feeding the fan(s) carrying the +12v and return for it. If they are too thin they may burn up.