Hello,
There is an inconsistency in the performance indicator.
I am using a Mac mini M4.
The higher the buffer size, the worse the indicated performance score becomes.
This is not normal. Could it be a bug?

The performance index should be quite stable, unless macos decides to throttle the cpu a bit more when you use large buffer. In the audio load curve, the change of cpu speed can be noticed with the small blue dots, if they draw a steady line then the cpu speed is stable, if they fluctuate a load then you os / hardware is adjusting the cpu speed (which is rarely great for audio applications).