Using this topic for another question: by default the region of Neo Geo games is in Japan. How do I set the USA region by default?
Actually the default is Europe/Asia, Japan is a separate setting

Load a NeoGeo game, go to the dips and set the bios to a USA version, then go to the inputs editor and hit save preset - this will save a neogeo.ini preset with the setting. It will then use this preset for NeoGeo games that aren't configured yet (such as, a game that has never run on your system, without he config/games/romset.ini file)
best regards,
- dink