What’s the difference of default vs energy saving in the performance settings? Both run at 1500 MHz and 500 Mhz core on ARM/GPU for pi4 b. The only difference that I see is the -2 overvolt, but what are the consequences?
Underclocking (lower voltage) = lower power consumption,
which saves energy 
I don’t get it. I mean, I get I lower the consumption but if the performance is exactly the same, why isn’t this the default setting?
Technically @MichaIng could explain it more in detail I guess
Lowering the voltage can cause instability and miscalculations. I think -2 where the risc is justified by the benefits.
But the vendors, like Raspberry Pi, want to maximize stability, even when the power draw is a bit higher.
Exactly what Jappe said: It is power savings vs stability. I never heard of a case where these -2 voltage caused any actual instability, but every single board/chip behaves a little different, so good to have it as option instead of as default.
Probably we can explain the impact of the 3 (4 on earlier RPi models) parameters.
Does this also mean less heat…? I mean, the clock will run at the same anyway, so I guess not.
Normally undervolting comes with better temperatures and/or better performance (Desktop CPU can clock higher when they have more thermal budget).
But I think the impact on the RPi ist not so strong and btw max temp for the RPi 4 is 85°C.
I reduced voltage on my RPi4B prod system to -2. After a couple of hours, temp still same at 42°C
5-7 watts vs 30+ watts or more…cmon
The very fact it’s ARM means it’s a power saving device…don’t mess with the power settings unless you lower the overall turbo (aka limit the highest cpu frequency the process is allowed to boost to under use)