It depends on what you want to do...

Do you want to sound as close to the record as possible, or do you want to forge your own path?

Either way works. One is more fun than the other, but riskier, as you might not hit the audiences' sweet spot.

But either method, I try to figure out how I can play the most I possibly can in realtime, and turn off as many arranger Parts as possible. There's a lot you can do by either setting up velocity switched sounds on one side of the split (say an organ part that turns into the brass section for ff hits) and layers (piano/chorus Strat for the left), or you can use your swell pedal to choose which of two sounds/layers you are playing by inverting the response on one of them...

Bottom line about the whole process is to record yourself. I often find that my on stage perception of a sound is colored by what else is going on. Only in retrospect, listening to it all while you aren't preoccupied with playing, can you decide whether your layout really works or not...

Hope this helps.