I didn't need to cut extra holes for now. It pulls in air from the gap around the door (not air tight) and it seems to be enough.
Concerning airflow over the heated bed, I don't print materials that require a heated build chamber. Then again, if I would I would just shut down the fan so the heat can build up. Mainly printing PLA, PETG and got some XT, XT-CF and NGEN from Colorfabb. I tried to avoid ABS (for obvious reasons) and no need for nylons.