Can anyone guide me to a study which indicates that high MP results in poorer IQ? PLS.
I cannot guide you to such a study and I am shure you will never find such a study because:
If the per pixel quality stays the same, more pixels give always better IQ until other factors like lens IQ are limiting.
Lower pixel counts help to reduce processing time and filesize which may be valuable for some purposes but nothing less/more.
I am physicist and it was never bad to measure values as precise as possible - it was bad to measure with less than required precision! If you don't need the precision you can report rounded measurement values - if a light bulb has a power consumption of 60.22412 Watts or 60 Watts essentially is not important for a bulb user, but perhaps for a lamp design researcher who optimizes the production process.