The I2C switch changes the master of I2C devices (gyro/accelerometer, servo driver, external EEPROM). On default “Arduino”, NyBoard uses the onboard ATmega328P as the master chip; On “RPi”, NyBoard uses external chips connected through the I2C ports (SDA, SCL) as the master chip. Always select "Arduino" unless you know how to connect the I2C devices from the external chip.