I'm wondering how much these silencing systems with a mute rail affect the feel since I believe the escapement distance is increased to allow for the mute rail to be inserted and stop the hammers before they hit the strings, yet have a working escapement.
In the Kawai upright and grand pianos featuring the previous ATX/Aures silent system, the impact was quite significant. In the uprights, the overall key travel is reduced in both silent and acoustic modes, even with silent system disabled. This means that playing a silent upright in acoustic mode is not the same as playing a similar upright without silent system. This can be easily checked if you go to a showroom and play for example a K500 upright without silent system and a K500 ATX/Aures. The difference will of course depend on how properly regulated the piano has been, but I the Kawai uprights (and other brands as well) I have checked in showrooms had major differences to their acoustic only counterparts.
With the Kawai silent grand pianos, the difference is more subtle in acoustic mode. There is still a difference compared to a grand without silent system, but it is not as noticeable as with the uprights. However, in silent mode, the key travel is reduced and the overall feeling is quite different (for example, the resistance at the escapement point is not noticeable).
As far as I know, only the Yamaha grand pianos with SH/SH2 silent overcome this limitation (note: Yamaha only uses this system in grand pianos, not in uprights). Yamaha call this mechanism "Quick Escape". It physically changes the geometry of the action and allows for separate regulation in acoustic and silent modes. The result is that the regulation in acoustic mode is exactly the same as in a piano without silent system and the regulation in silent mode feels almost the same as in acoustic mode. Hopefully, Kawai has done more than just a software/sound engine update and introduced a similar mechanism in this new version of their silent system.