For a very long time now, it has been the case that in the short term most processors will boost high enough for the die to reach around 100°C. When you see a reading substantially lower than that like your example of 75°C, either the system has throttled for a reason other than processor die temperature (eg. throttling to limit the temperature of the outer case of the machine) or the temperature reading you're seeing does not correspond to the hottest part of the chip and the throttling is based on the presumption that a different part of the chip that is not directly monitored will be much hotter.

In the specific case of the i7-7700T, the "T" suffix for Intel CPUs usually means you have mainstream desktop silicon with arbitrarily reduced long-term turbo limits, intended to be used in small form factor PCs with limited cooling capacity. Its limitation to 35W sustained and official Tj max of 80°C are artificial and essentially fiction, and the same silicon will readily do 91W sustained with a Tj max of 100°C as seen on the i7-7700K.

Processor temperature under load tells you almost nothing about the power draw or efficiency of the chip, because the temperature can be controlled to almost any value desired through a combination of varying cooling effort and varying clock speeds.