What is max safe temp for DDR4 ram and max safe oc voltage for DDR4 ram?

[OIympicAssEater]

What is max safe temp for DDR4 ram and max safe oc voltage for DDR4 ram?

[_I_]

oc ram is nearly pointless
most ram does not like to be oc, if it could run faster they would have binned it faster
raising the freq also means you need to raise timings (freq / cl = performance)
ram voltage can also harm the cpu since the imc is on the cpu

1.2-1.3v for most cpus with ddr4 imc

performance gains are small compared to cpu/gpu oc

if you need faster ram, buy a faster ram/kit with lower timings

[L37]

Well, since all the kits are just binned overclocked chips... some people prefer to buy simple non-kit sticks without xmp and OC it themselves. Results are often pretty good.
For safe temps/voltages it is usually possible to find datasheets for specific chips used (but you have to read chip model and google it, not stick model).
Apart from info there, as mentioned above, you should also take into consideration what voltages are safe for IMC, which can be different for different CPU-s. There is usually no official info on this, so you will have to rely on stuff you can find online...