Within the Wiiflow/plugins folder on SD card I assume, that's where all the others are.
The NES games say the plugin to be used is FCEUltraGX and there's an fceugx-mod12.dol file and the fceugx.ini file, which shows:
[PLUGIN]
displayname=FCEUltraGX
magic=46434555
coverfolder=NES...