Here's an old build out I did. The fan on the PSU is there and is part of the ATX specification. The extra fan is not part of the specification. It can be removed and the case will still be an "ATX case". The CPU is sitting next to the PSU fan for a reason. It would be the only way a passive heatsink would get sufficient airflow. They could have moved the CPU further away from the PSU, but they put it there for a reason.
This machine ran overclocked at 133%. This arrangement kept the CPU cool enough. Well under 100 C.