There is still a lot of speculation and guesswork when it comes to corrugation (and polygonization of wheels). The causes and effects are still not completely understood.

They say that certain rails (profiles) tend much more to corrugation than others, and that certain combination of wheels and rails have a higher tendency for corrugation.

Research is ongoing, but I am not aware of any conclusive results.

With micro-slip, I am not sure whether wheel or rail are plastically deformed; I think it is still in the elastic range. Keep in mind that micro-slip occurs with speed differences of less than 0.5% or so.