Ok, because we can't measure the current that goes through the processor and deal only with the voltage, which is basically the same thing given they are direct proportional, can I raise the voltage over 1.5v as long as I keep the temperature down under stress with an adequate cooling system, let's say below 75C?It's both current AND temperature. The way to reduce temperature at a given clock, though, is to lower voltage.
As far as voltage, the only thing I've ever seen from AMD about a safe voltage is to keep it in auto, let the processor determine what is safe for itself. It automatically reduces voltage, AND clocks, to a safe level based on temperature. If you've ever heavily stressed a Zen2 processor at a heavy load (like Prime95, small FFT, AVX) when in full auto, no PBO, you might find it lowering voltage down as far as 1.2 volts, with a clock speed right at or just above it's spec'd base frequency. That's about the best way to figure what's safest.