What exactly happens if the operational temperature is exceeded and the psu has OTP protection ? Does the psu stop immediately or functions but at a lower efficiency or the continuous output falls ?
OTP (Over Temperature Protection): Shuts down the power supply when the internal temperature exceeds the maximum safe operating temperature.
That seems pretty clear. It will simply switch off.
You very probably wouldn't want a PSU to drop to lower voltages or even ampages. That may be somewhat chaotic.