My pc started life as the middle one, heat soaked terribly in the summer with water temps getting to 42 degrees C on the hot days (mind you the main game I play is optimised like garbage). Forget heat rising and all that, if you’re exhausting one radiator into the intake of another it’s always going to be sub optimal.

Changed setup to the one on the right and dropped around 4 degrees coolant temp on the hottest days. Be aware if your pc sits close to your hand you will feel a bit of heat from the exhaust, I just installed a small barrier where my hand goes past.

Left side would also be a good option if you have other air cooled components in the case you are worried about absorbing some of the warm radiator exhaust air