Ok, in theory a geo-referencing should be possible the way you described. But where did you input the camera locations? It is similar to a multi camera rig workflow, by using XMS files (I think). In any case, the fact that it is different shows that it is not (yet) successful. The orientation is different each time because RC can only guess how big it is and which way is up and it does this differently each time. In my experience it works better if there is sky involved, but that might be my imagination.
So a mounf of cotton is still pretty similar to a wig :-) as in that it has very fine features that you need to capture in your images for the alignment to work properly. What I meant by the coverage is the percentage of area that your cotton mound takes up on your images. It should be the majority because with the black background RC cannot calculate anything and that means that for large parts of the images it’s just guesswork for the proper lens distortion.
Not quite sure what you mean in the last paragraph - you can activate it in the image menu and look at the distortion grid. Sometimes, there are some cases where the distortion is completely wrong. Ideally, if you shot with the same settings, they should be more or less identical. You might get better results by using exif grouping (if you haven’t already done that). If you are not sure how that works, a quick search here will provide you with ample reading material… 