Simply put, undervolting is mostly about reducing energy consumption and heat. If you can undervolt but don’t, you’re wasting energy.
Every processor of a given make and model will have a different minimum required voltage to run stable at the advertised speeds. Instead of bench testing every one, which would be extremely time consuming and expensive, manufacturers run a higher voltage known to work across the board and call it a day.
So to confirm: unless your CPU is running at 95C and being throttled, undervolting won’t improve speed or frame rate? But may be desirable for noise reasons (reducing temperature → reducing fan speed)?
Undervolting has allowed my CPU to hold its maximum speed on all cores for far longer when on final.
Previously, when at stock settings, frequency would drop on approximately ⅓ cores at any time and rotate through them when I least wanted it to, despite my CPU being nowhere near its thermal limit.
That said, @BegottenPoet228 's earlier comment is correct. Need some statistical analysis to support this assertion. Yet, on empirical evidence (gathered by me and sample size of n=1 
), this is a repeatable finding.
Yes I would say also in my personal highly scientific evidence of “how it feels”, undervolting my CPU was the final big tweak that truly unleashed some extra smoothness and the potential of my setup (7950X3D).
It was fast and easy to do just on “safe global numbers” and I could not have done it without help and reassurance that what was being configured was correct and safe, but it definitely helped make everything more punchy.
In the Curve Optimiser I set:
Cores 0-7 at -20 (the vcache chiplet)
Cores 8-16 at -15
The real pros spend weeks tuning each individual core to its limit but I can’t be bothered with that!!
This needs to be redone after any Bios updates so I wanted just a fire and forget solution.
EDIT TO ADD: I think it’s important to add that this works in conjunction with enabling PBO so that it boosts more often/higher and a manual temperature limit for throttling. I have set that manually to 89 degrees.