The ROM Performances tend to put all Part Volumes to 100, so that seems a good place to start. If a user style is out of whack at those settings, the best solution is to Makeup Tools the style so it sounds balanced at those volume settings. Now you can swap between user styles and factory styles and your balances should be consistent. Me, I tend to push the ADrums and ABass a little hotter (110 or so) to get more of a live band feel, but you probably have your own preferences..!

The larger problem is that you still seem to want to swap styles in and out of the same Performance, rather than the far more comprehensive solution of creating a Performance with the new style. If the two styles are something you tend to switch between on the fly, place them adjacent in the Perf. List…

With as many styles available, and navigation in the user style section buried so deep in the folder structure, the Perf. List seems such a simpler way to get at needed styles.