The Tyros4's style part on/off screen has icons for each instrument (and a light that comes on under it when it's being played)...a bit helpful, for sure...if I can remember to shut that part off.

What I also have done with some styles, and instead of replacing the string/synth pads, is to turn up (volume) those particular parts, rather than use a pad/string sound in my left hand which tends sometimes to sound too dense and/or muddy.
Quite often these style pad parts default at a volume a bit too low for my liking. Once I get a mix that works, I'll re-program and store the style with those settings.
Now that our instruments have basically unlimited storage, and, if you don't mind doing a little more planning ahead, the shutting off of style parts can be accomplished even easier by programming a set of eight registrations to accomplish that function for that particular style and/or song.
Ian