Thanks for the pictures. Don't forget to put a bit of electrical tape onto the PCH to correct the emissivity (read for short explanation and good post by FLIR on how to correct it).
About the power design of this motherboard. It is certainly not a usual layout and I don't yet fully understand how exactly it works (I don't see enough MOSFETs for example). I am however pretty sure it is properly cooled and doesn't need a heatsink as long as there is some airflow and the case temperature isn't too high.
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Asus STRIX Z270I:
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Good call on the electrical tape - I ran into a similar issue measuring a motor the other day.
The part you called out in question has a reference designator of PDQ1321 and a label 'R10 647 CBL'. And yeah, not sure where the last mosfet is for that inductor, although one of the inductors at the other end has three mosfets close to it?