guideline for liquid cooling is a 120mm fan per component. Does the same apply with these?
that really depends on the specific component.
an 11700K can run quite hot when boosting to 5GHz, so it may take 3x 120mm or 2x 140mm for good temperatures.
and an RTX 3090 is the same scenario.
to allow it to boost to it's full potential and remain there you would want it in the 60s - low 70s°C at the highest.
this could take 2x 120mm.
then you've also got to figure that there would be enough cool air being brought into the chassis to offer enough for the radiators to pull in and benefit from.
do you have any previous experience with custom liquid loops?