If you want max airflow, then you'd be best off sizing 1 fan to be as large as possible given the motor size/power.
If you want operate several small fans in different locations, then you should have a small motor for each one. The motor is always going to be smaller than the fan blades, and transferring power electrically is much easier than any system of belts or gears.
thanks Mrparkle for your reply. i meant in a small scale. how can i use one motor to spin several devices, it doesn't matter if it's a fan or something else.