Yes, it definatelly matters.

Heat rises, so putting the active (fan forced) exhaust up high, is best.

Passive (no fan) intake near bottom, but be careful of light leaks from both. Not necessary to cut that big of intake holes. You can likely get away with smaller. (2")

You'll need a circulation fan for inside the cabinet, too. (exhaust and intake don't work well alone, so additional air circulation is needed.

Have you taken a look at other wardrobe conversions, for guidance?