Some instances of chrome are special instances, like rendering and GPU acceleration, and thus will appropriately use a higher priority. If they are unusually active, you need to consider what sites you are visiting and/or what Chrome extensions are in use.
Chrome has a built-in task manager that may help.
Forced Mode in combination with a persistent priority class would cause ProBalance actions to be immediately undone for target processes. However, that would be an odd use of it - it'd be better to simply exclude those processes from ProBalance.
In the end, I am doubtful that you'll derive any performance improvement from fiddling with the priority classes of your Chrome instances.