Finger touching ( carefully ) all areas of the MD do not reveal any hot-spots and there appears to be plenty of cool are passing over the MB.

CPU is a 9900K, liquid cooled ( dual 140mm fan ) + 3 140mm case fans.

The only difference that I have with this build is that the MB is inverted as I have my window on the right of the case.

I often find when boards are not properly supported on third party monitors you get a few bogus readings. Generally speaking, if ASRock's A-Tuning utility shows your temps are fine then all is well. It is designed to work with the exact sensor setup for your board. Generally the 3rd party apps get updated and these issues are sorted over time. I prefer using HW-Info, it's more comprehensive but early on with many of my systems (early adoption) I had high or drastically fluctuating data using it.

Check in A-Tuning and see if all is well there, if it is, odds are it's a false reading. Wait a month or 2 for the monitoring app you have to get updated properly for your board if you prefer it to the bundled A-Tuning app 

I think you are correct, Corsair iCue is showing 60c ( now 65c ) but HWinfo gives some really strange readings. AUXTIN1 is reading 108c whilst AUXTIN2 is reading -119, yes MINUS 119!

As I wrote in my OP, finger testing shows no hotspots either. The warmest thing in there is a soundblaster z.

Obviously still too new for the software to have caught up with the hardware.