There are so many aspects to perf, there’s no one thing that will show your computers limits.
You buy a new fast computer to do a specific thing. Time it doing that thing, that’s the best case.
A lot of modern high end computers can’t cool themselves adequately, fans run fast and then they’re thermally throttled. Whatever you do, run the test a while so you can see the perf when it’s heat soaked.
Here’s a good write up:
https://www.tomshardware.com/reviews/stress-test-cpu-pc-guide,5461.html