VRAM temperature is also important, and most of the time in my experience, its about 15-20 c higher than core temperature.
VRM - Voltage Regulator Module, to put it simply the 1st place where electricity passes before it reaches gpu core and other modules on the card, obviously it takes more heat than core since it's job is to give as much power as gpu core asks, as you said 10-20°C warmer than core.
VRAM is video ram, usually gddr5(x) or new the hbm(2) on fiji/vega gpus, they don't generate that much heat to be of a concern