AFAIK there’s no way to erase the plocks on the steps all at once. If things get too crazy I usually turn the two knobs to the center position without pressing any buttons. Then I press and hold the write, while in “play” mode, and twist the knobs ever so slightly. This overwrites the parameter on all steps eventually. That’s kind of a workaround though you have to be very quick if you want it to be unnoticeable.
For most of the synths I don’t actually mind the different effects the parameters have when switching to another synth. If you plan ahead and know that your’ switching to one of the synths in the lower half of the PO you can start bringing the parameters into less destructive ranges beforehand. Or you could try adding an effect like any of the filters to ease the transition while you re-adjust the knobs.
The micro drum machine behaves in the very same way: Each step has a saved parameter setting. The only difference being that you can assign a different drum-synth to each step.