Ryzen CPUs have a few dozen temp sensors across the core die and the I/O die.
CPU (Tctl/Tdie): Its the highest temp of the CPU. The hotspot. This reading is constantly switching to the highest reading sensor and reports it. "Tctl" means temp control. Its used to control the CPU fan. Its unlikely that the I/O will be hotter than core die at any point, so this reading is pretty much switching between core sensors.
CPU Die (average): Its the average of all sensors (probably) across Core/IO dies.
CPU CCD1 (Tdie): Its a reading from a specific sensor on a specific location on the Core die. The edge temp.
In idle/low/light loads you will see differences between them. But when the CPU is fully loaded all readings should be close to one another. So it does not really matter what reading is used for throttling. I believe its the Tctl/Tdie though. The throttling point is 95°C but Ryzens (ZEN2/3) are cutting boost before reaching that point. Keep it as cool as posible for maximum boosting.
It will boost differently at 65°C, 75°C or 85°C.