Should I go by vcore or svi2tfn In hwinfo64? I didn’t ask how to oc I asked about voltage readings.
Yes, that's the voltage reading at time of measurement you should go by. Keep in mind that it's a highest reading for at least one core at that time, not necessarily all of them, for all you could know it could be for only one (most loaded) core. Even if relatively high it may be only a transient voltage and main concern is the Average value, same goes for temperatures.
If all is left on auto (no OC or permanent settings) that can wary quite a bit because of XFR and PBO. Other values to look for is Wattage, per core and Package. Even if 100% on all cores is indicated, not all programs and even benchmarks would produce highest wattage reading and Wattage is the value that produces heat.