I'm puzzled as to why you prefer stock settings and why you're using the thermal threshold of the GDDR6X memory as a guide to whether or not your GPU is doing 'fine' with respect to temps. Undervolting should net you better performance (by allowing the GPU to boost higher) with lower GPU temps and fan noise. Lower GPU temps should also lower overall system (incl. CPU) temps given the flow-through cooler design. At 83 C, your GPU is definitely dialing back the core clock to remain within acceptable temperatures. Run a 3D Mark Port Royal benchmark with HWiNFO64 running in the background. HWiNFO will let you know if your GPU is throttling or not (my take is that it definitely is). Also, compare benchmark results pre- and post-undervolting to get a handle of much of a difference it can make.