I bought a MacStudio 2 months ago, on Sequoia you go to "display" and should see the various resolutions. If not, "advanced">"show resolutions as a list">"show all resolutions".
My 2019 Mac Pro with Catalina could happily drive 2 4K monitors in HDR @ 144 Hz.
People wondered how Apple got the math to work to drive the ProDisplay.
Big Sur? Not any more. 95Hz for 4K SDR, 60Hz for 4K HDR. Not the cables, not the monitors. Indeed, "downgrading" the monitors advertised support to DP 1.2 gave better options, 120Hz SDR, 75Hz HDR.
And it was never fixed, not in Big Sur, Monterey or Ventura, when I had switched monitors.
Hundreds of reports, hundreds of video/monitor combinations.
"a hurried, wild, or desperate manner, often due to extreme worry, fear, excitement, or panic"
At some point this frantic nature of trying to do something will cause more issues all by itself.
Instead of spending hours in desperation, I was only suggesting taking a step back and maybe when not in a frantic state, it would be easier to move forward.
The third party software is really good, but come on, Apple, take a hint.
And, as I said, I really only needed the software once I got an (ultra)ultrawide monitor, and it could be the info it is sending is also non-standard in some way.
I doubt anything is going to get fixed, and Apple's hardware crown isn't as strong as before. But they like selling "services," so...