We are going around in circles here!
Original question - how can you have 3 different CMs for the same airfield, same a/c Cat?
Q1- can circling area geometry vary for the same airport and same aircraft cat - and how?
a) I assume you take the obstacles within the altitude adjusted radius and add 300'?
b) If this pushes the CM into the next altitude band, you redo it at the new radius and iterate if required?
There we are - 1 CM surely?
Q2 - RNP/CTL?