Thermal protection is based on Intake Air Temperatures, it part of the mapping, on stock ECUs.
This protection helps keeping your turbo/engine alive, because with raising intake air temperatures, also the exhaust gas and combustion temperatures raise, decreasing the combustion efficiency and the amount of fuel which max. can be burnt. (Thats why we always want as cool Intake Air as possible)
I have seen very very many chiptuning files where this protection was disabled, taking the risk of causing damage to the customers engine, like turbo failures per example. (Only to name one single mistake what is common in tuning softwares...there are way more than that...)
Anyway, if you are a lucky guy with a chiptuning file WITHOUT this mistake, then your car should loose power when flooring it longer. This maybe sound kind of "No, I dont want that" BUT it protects your engine from blowing up.
So if your software reacts properly, THEN you will have a benefit from a bigger FMIC, because it will hold up full power for longer while flooring it.
Actually the power reduction begins at about 50-60degrees celcius which is reached pretty fast with high boost and small SMIC.
The Garrett Turbo has a better compressor map and a better turbine, so it will from beginning PRODUCE less heat than the kkk kp39.
Greets, Alex