look in HWInfo for a "VR VOUT" sensor. Some boards don't have it but if you do then that's what you should be looking at.
Software readings always have some level of inaccuracy but the VR VOUT sensor is a direct readout from the VRM and should
be accurate enough.
vDroop is normal and it's a good thing (albeit annoying), use LLC to limit it if it's excessive but you shouldn't try to completely remove it. Overshoot is more of an issue than needing slightly higher voltage to offset the vDroop.