the legato mode is actually the same mode than when perform was OFF in previous versions. We needed a specific mode to attach the quantize and latch function (and a place to hold the options in the UI). So we renamed the “OFF” mode to “legato” as it plays full chords for the entire “chord duration” or the entire length of your trigger-note (compared to other mode which explode the chord and play shorter notes).
It is normal for the legato mode to turn off when changing to Expressions.
You are right, the improvements to the timing make everything slightly smoother, getting rid off the irregular (tiny) offset we had in the previous playback really made things better and noticeable if you have a good ear for timing.