>>106508514
Most of the GeForce undervolting guides on YouTube make the card run power inefficiently @ lower voltages.

Download this latest beta version of MSI Afterburner.
https://forums.guru3d.com/threads/msi-afterburner-4-6-6-beta-6-with-unofficial-rdna4-support.456792/

For the simplest OC+UV, raise the [Core (MHz)] offset slider in the main screen of Afterburner between +120~150Mhz.
You can start at around +180~200MHz offset for RTX 50 cards (they have more overclocking headroom).
Then lower the [Power Limit (%)] slider to 70~80%.
You're not voltage-capping the GPU with this method, but the lower power limit will restrict the card from requesting high voltages.

If you want to actually voltage cap the GPU, follow this guide.
https://www.youtube.com/watch?v=LPpW9yXHvOU
The video raises the GPU core offset like I suggested earlier, and it modifies to curve to cap the maximum voltage draw.
Read this guide for details & how to apply & save changes (including applying preset on Windows bootup).
Don't set the OC+UV profile to apply on Windows startup until you've run plenty of stability test (gpu demanding benchmarks & games, including RT tests).
https://github.com/LunarPSD/NvidiaOverclocking/blob/main/Nvidia%20Overclocking.md

You can also OC the VRAM [Mem (MHz)] slider to around +800 MHz for RTX 30 & 40 series cards, and easily past +2000MHz for RTX 50 cards.

>>106407651
The easiest way is to set a +200MHz offset using the GPU Core (MHz) slider in Afterburner, and lower the Power Limit slider (anywhere between 75~85%).
You can push the GPU Core offset a bit higher (in 15MHz increments), but it might get unstable.
You can set a voltage cap using the Curve Editor, like in the video below (flatten the right side of the curve).
https://www.youtube.com/watch?v=LPpW9yXHvOU

925 ~ 975mV is the performance/efficiency sweet spot.
https://github.com/LunarPSD/NvidiaOverclocking/blob/main/Nvidia%20Overclocking.md#undervolting

You need to use the beta version of Afterburner to unlock memory OC past 2000MHz.
https://forums.guru3d.com/threads/msi-afterburner-4-6-6-beta-6-with-unofficial-rdna4-support.456792/

>>105733056
You just have to move like 3~4 sliders in Afterburner, save the profile, stability test it, then set it to apply on Windows boot up.
I would start with +120~150MHz GPU Core offset, +1500MHz memory, and drag the V/F curve down at 900mV or 950mV (lower is more power efficient, higher is more performant).
The OC offsets can go higher, but higher values are less likely to be stable (stress test required).

This video shows the process, slow it down if it's too fast.
https://www.youtube.com/watch?v=LPpW9yXHvOU
https://github.com/LunarPSD/NvidiaOverclocking/blob/main/Nvidia%20Overclocking.md

The guides shared by techtubers can make the lower V/F points more power inefficient.