Right now, not many people have Zen3 CPU's so not a lot of forum traffic on them. But the 'safe' thing is simple:
Keep your board's BIOS up to date as AMD is releasing AGESA improvements that can be significant to performance and stability.
Install the latest AMD chipset drivers downloaded from the AMD web site to make sure they're the latest too.
Run VCore voltage and VCore frequency in AUTO for now. You can enable PBO but you'll probably need pretty good cooling...a lot better than the stock Wraithe that comes with 5600X's. If you want to experiment around with manual fixed overclocking go ahead but you will again need much better than stock cooling to keep temp in control.
And again, with not much forum traffic on it, what's 'safe' as far as voltages go just isn't well known. Experimenting with under-volting using offsets sounds like a really good idea, especially coupled with PBO. Just be sure to measure actual performance in addition to stability... and especially single thread performance... as you're doing it.
Also enable XMP or DOCP or whatever it is called on your board for memory overclocking.
Let us know your experiences.