Spent a couple hours speaking with 3 levels of Apple tech support. They each confirmed that when running most "heavy" video games, the Activity Monitor, etc. GPU readouts will show a constant 85-100% processor usage, but that is not a problem and doesn't indicate that the GPU is out of processing capability.
The question they could not answer is how can you measure/monitor when/if the GPU is over-pressured (since it will always show a "normal" 100% usage in a "game"). While you can in Activity Monitor view a graph of GPU History, it is a flat line of a maxed out bar graph (which, I'm told, is not an issue nor indicative of overloading the GPU in these Studio models). The numerical readout also doesn't seem to evaluate whether there is too much pressure on the GPU (according to the 3 tech support people). iStat also doesn't have any real detail other than the processor is at 90-100%, whilst the cpu and RAM is under little pressure.
I did come across a small Python tool that provides a bit more detailed view of computer performance in a graphic view in Terminal (called macmon). In the X-Plane newest betas eventually constantly crashing due to cummulative GPU problems in flight, that utility will show very, very low CPU use by both efficiency and performance cores, low RAM use, no temp or power issues, but it does show GPU at 95-100% processor usage (which, according to Apple techs, is normal and okay).
Interestingly, macmon does read out the GPU's processor percentage but also at what MHz (and it is normally quite low). None of the 3 tech people could answer whether seeing an ever-increasing MHz reading for the GPU would indicate a building GPU "overload", thus explaining the eventual accumulating GPU overload and CTD in the new XP betas.
Now the question becomes: How can a person monitor actual GPU possible pressure/overload if the GPU usage readout is okay/normal at 100% in a video "game" app? Are there any other tools/diagnostics out there that can watch for an overloaded/pressured GPU situation in a Mac Studio? As we all know, back with the Intel Macs with standard video cards, it was easy. Watch the video card's processor and VRAM usage and easy to spot an overloaded/pressured GPU. But with the new ARM units, even 3 Apple tech people (each at a higher level of support) couldn't answer that question.
Hopefully someone knows how to do this???