Thanks.

At first i was doing 630 with 1.76V set in bios so 1.73V real and it was stable.

After that i tried 632 because i wanted to go under 10 minutes (Low Clock Challenge) and got some errors so raised Vnb to 1.8V in bios and still got errors now and then.

After some more testing it dawned on me it was caused by the maxmem setting combined with Copy waza.

Still left it at 1.8V, which resulted at 1.78V in windows approximately.

With the EK NB S-max block temps never went over 34ºC though.