Mine ran fine with Kato U30Cs and SD45s, all several years old. Not exactly the same speed, but they didn't seem to fight each other, and they stayed coupled. The three made several laps of my old-fashioned DC layout, in both directions, with the U25C both leading and trailing, with no apparent problems.
We had quite a discussion on the issues with the U25C, all of which seem to have come down to assembly problems on the NP units. If you have another road, you shouldn't have any problems, based on the comments in that topic. If you have an NP, you may, or may not, have to do some work on the pickup system. Out of the box, my NP units ran slower than the others, when they ran at all. With a little work, they run as well as the others, and it was one o f them that I tested the MU operation with.
I only have one Atlas "slow" motored unit, and it isn't intended to be run with anything else, so I didn't unpack it to test.