The reason SM needs a change is because of the way SM's scripting for summons was written and how that interacted with MOO's region specific summons (where you got things like Argonian zombies and skeleton summons if you cast the spell near Black Marsh). It was a pretty unique issue and specific to SM, so I doubt you would have the same issue with MRR. It is also easy to fix by making a minor edit to SM's scripts. Maskar provides instructions for how to do this. Or you can just disable the region specific summons in the MOO ini.
I was actually the one who first discovered the MOO/SM issue and I only discovered it after playing with both mods for a few weeks. Once I discovered the problem and pointed it out to Maskar, he was very quick to come up with a solution, and I have not had any issues since.
I doubt you would run into issues like that with MRR, but unless someone has run these together you won't know for sure until you try.