I've tried the Rapid Fixer + citric acid bleach on c41 developed in rodinal.
remember that your image in C41 monochrome developed in rodinal is still formed from silver, so the bleach will reduce the negative image as well as reduce the mask.
So you can easily end up with quite thin negatives, and, in my experience, rather patchy density.
BW400CN is a nice film when paired with the right paper, same for XP2.
XP2 was designed from the start to work with normal B&W paper so it never has a mask, regardless of how you develop it.
The BW400CN was designed to print on color RA-4 paper so the mask was designed to be permanent, regardless of how you develop it.