Max coolant temp- what’s the worse that can happen

Prius over-temp sensor lights up the dummy lamp around 245F+. Slight deviations above 205F-210F are normal under heavy load; as long as it falls back down to normal operating temps, once the additional load is relieved.
IMHO; It's the constant operations of the ICE near or around 230+F that causes blown head gaskets, warped heads and sometimes boiling out the coolant. This all happens w/o the dummy lamp lighting up and no stored CEL for overheat.

 

I have to kind of translate your numbers into Celsius, because the car's Japanese so of course all the interesting points programmed into the ECUs are easy-to-remember numbers in Celsius: fans turn on at 95℃, red temp light turns on at 120℃. Engine stops if the water pump isn't working at 105℃.

That last is kind of an interesting case. If the ECM has an active water pump trouble code, and the temp reaches 105℃, it turns the engine right off, no discussion. The power management control ECU won't even know what happened: it'll log P0A0F (hey, what happened to the engine?). But that only happens if there is already a water pump problem that the ECM knows about. Otherwise, nothing of interest happens at 105℃ or until you see the red light at 120℃.*

I don't know if there is any other special action taken at 120℃ besides turning the red light on. The only automatic engine shutoff I know of is the one at 105℃ if the water pump has problems.

People on PriusChat use the term "limp mode" for a lot more different scenarios than Toyota does. The absolute engine stop at 105℃ leaves you completely dependent on the battery for moving the car. If you have ever played with the "EV" mode, you know the battery in the best case can move you two or three blocks at under 10 MPH. If the engine stops cold while you're doing highway speed up a hill, you'll be out of battery before you know what happened. You might have technically been in some kind of limp mode for 20 feet or something, but you won't call it that, you'll call it dead in the water.

Your temps of not even 98℃ are just a couple degrees above turning the fans on. That wouldn't worry me,


* I'm using 120℃ for where the red light comes on based on a test I made on the second coolant temp sensor, the one in the EHRS return hose. I have never actually done the same test with the sensor that's in the cylinder head: I'm assuming the same alarm point of 120℃ is programmed in for that one too, but I don't know this.