You might look to see if there is an Appendix at the back that tells you the changes that were made between the RSV and the RSV CE (at least in the NT). Some of the text and footnotes were swapped for the Catholic Edition, when both translations are supported.
One example is the brothers vs. brethren issue. In the Protestant version, it is brothers, but in the Catholic version it is brethren. Both readings make sense because (as I understand it, I am by no means a Scripture scholar) the Greek technically means brothers, but Hebrew, and also in Aramaic (the first language of most of the writers of the NT), the word for brothers has a much more broad connotation more like “make kinsman” which makes brethren possibly give a more accurate feel for what the writers actually meant.
However, there are probably huge threads on the brothers/brethren question on these forums, and as I said, I am no expert. So I really don’t mean to start that hare, just to give an example of the kinds of alternate readings that might be switched between the regular text and the footnotes in the Catholic Edition.
Anything that isn’t mentioned in the appendix (at least in the NT) is not related to Catholic/Protestant.