[cflsystems]

It will affect all of them yes but you can limit which ones are affected with your custom module. In XC5 you can't just go an change some code - it has to be done with a module or you lose changes on next upgrade.
Also - this will not have any affect on which option is selected on page load if its value is passed. It will only be the first one to start with if no option is selected by default.