you've reached the philosophical fundamentals of airflow, that one may ponder upon in order to yield the physical exponents relative to the structure and flux under which forms are naturally transformed and induced upon the very nature of form blending into natural harmony
in otherwords, all you need to consider is this:
Physics law
hot air goes up, cool air goes down
you need to side with physics and don't go against it
both of your options, A and B aren't natural
you have the following options always around the same framework and structure pictured, no matter what case you have
A) intake from the front either bottom/mid or bottom/top, 1 case exhaust rear (the most logical choice)
B) 1 intake from below, 1 intake from the bottom or mid, 1 exhaust rear (favours GPU since the card has an exhaust on the side)
C) 1 intake on the front bottom, 2 on the top exhaust
(best cooling since larger surface and air goes directly on top)
In the event you have a radiator, it's best you always push out the electrostatically charged air (not pull in radiator air)
Check the side of your fans, you will see two arrows, one which way it spins, one the direction of the airflow. I would recommend to flip all fans, aka the fins should always spin upwards to push hot air out (see physics law), by preference.
Check the length of your fan connectors and if your motherboard has CHA_FAN 3 pin or 4 pin, 3 pin is direct current and 4 pin is PWM which dynamically adjusts, I'd recommend following the charge according to the pin of your fan but normally you can leave default settings.