Hi.
Just like you i use round cables as much as i can in my A4000 (for IDE and floppy drive to my bridgeboard) but i am stuck with the ribbon cable for the Amiga floppy drive.
That is still a nest unfortunately, because a SATA to IDE adapter for my SSD add to the bulk and several cables are crossing themselves on top of the accelerator (CS MK2 68060 with fan here).
My zorro/isa slots are all full, so i can't have a blower fan like you there.
Hence, the A4000 has only the CPU fan and the PSU fan which is also a Noctua blowing to the outside.
I can tell with ZZTop that my ZZ9000 chip is running about 72 to 75 °C (i have seen about half in A4000 of other guys), but everything is stable nonetheless, including during hot summer, and in general i prefer silence over airflow.