From: United Kingdom
In the PC case, the PSU normally draws air out of the case, so there is warm air at the rear, therefore all other rear fans should draw out as well. Heat rises, so a top fan (blowhole) should draw out as well.
Therefore, unless you use a lot of passive vents to allow incoming airflow where it's needed, all other fans should blow in.
Where you do not have that constraint - as you describe...
An incoming fan delivers a directed blast, effective if aimed at the parts requiring cooling, less so elsewhere.
An extracting fan removes air from the immediate vicinity, replaced by a lazy flow from elsewhere - if all availble designed and incidental vents are more or less equidistant, and of an area not significantly larger than the fan, then a relatively even flow should occur (avoid vents close to the fan, or make them small, or they will steal too much of the flow.
One example, some mini desktop systems had open speaker grilles close to the internal intake of the PSU - they were grossly unreliable in summer. Taping up the open speaker grille brought instant relief, as the airflow was force to go via the grilles on the other side of the case.
By the same token, if a case had two rear fan positions, and I only used one, I'd block the other