Using both intake AND exhaust fans is a waste.
In fact, if your "cutouts" on the miners are tight enough, you might not need additional fans at all - the fans of the miners should get your air circulation going.

 You WILL need more space for air intake and exhaust though if you are planning to run 600 AMPS worth of 220V mining in that room - most likely you'll need to replace BOTH windows with louvres or some such.

 Breaker panels on the cold side and well away from the window is a VERY GOOD idea - don't change that part, except perhaps to put ALL the panels on the back wall not just 2 of the 3.
 Breaker panels CAN be mounted in a vertical stack, if you leave enough space between them for wiring access - the code spec for "required height" is pretty wide.