using "game default" means that it's "forced to the game's region".
if the game is PAL, it use "force PAL"
if the game is NTSC, it use "force NTSC"
etc.
It's the mode you should use by default for all your games, it's setting the wii to the correct mode so the game can be displayed in it's native video mode/color system.
so it's forcing the Wii to be set to PAL, then the game launches and see the console is PAL so it pick PAL video mode from it's compatible video mode list. (but your TV might not work with the internal video mode that the game select)
the game probably doesn't contains NTSC video mode at all in it's internal compatible video mode, that's why it hangs (or just black screen).
There's a way to add the missing video mode (it doesn't work every time, but it's worth a try).
I'm sorry I don't know CFG Loader settings, so I'll tell you with the loader I know :
run USBLoaderGX and select the game
go to Option > game option
dol video path : set to "All"
Video mode : try Force NTSC
with this setting it will set the Wii to NTSC (which is it's correct region) and will patch the game to replace all PAL video modes to NTSC too.
When the game will launch, it will look into the list of compatible video mode (all ntsc now) which video mode matches best your current Wii video mode (NTSC too).
if it doesn't work, try other video modes.
if none work, I'm sorry that PAL game will probably never work on your NTSC console.
