Can I use multiple configurations to launch GameEx only for Games or only for Karaoke and so on?
Yes, GameEx has command line support, so you can create shortcuts that launches GameEx with different settings, like with the screen rotated for a vertical monitor, just for HTPC use, etc. Example: Make a copy of your gameex.ini and rename it to allfeatures.ini or something. Then turn off all your settings in your original .ini to create a light version.