For long term use, I'd suggest not going over Vcore 1.4V.
At Ryzen 1st gen launch, an AMD video suggested a max SoC voltage of 1.2V, but this could be outdated now.
Because you've got the R5 2600, you'll mainly be using the SoC to stabilise the RAM overclock. Try SoC 1.1V and see if that's ok, as you're unlikely to need much more than that.