Well there are many factors at work. Your old powersupply actually had more than enough power, the new one might just have better ripple surpression and thus delivering cleaner power to the VRMs.
First of all 81 is perfectly fine especially for the 12-Core variant on just an AIO. They can take a lot (104C if temp limit is raised) since you don't put the same load on the chip 24/7 as benchmark/stresstest tools like prime95 do all the time. If you hit 5.1Ghz that's pretty damn good. But you don't clarify if this is only CB R15 stable (benchstable) or rockstable.
Anyways to give you a quick guide for the platform.
Raise Vccin to 1.95v (up to 2.1 is save to set and forget, but I'm a bit more conservative, so raise more if needed to get your R15 scores up where they should be). That is to provide the needed power to the integrated voltage regulators in the chip (IVR). If out of balance (to low) when overclocking you wouldn't necessarily see instability but CB R15 would give you a lot lower Score (kind of throttling but kind of not since it's this time not heat related).
Start out with Vccio and System Agent Volt at stock (not Auto, figure out the stock values, XMP tends to raise them unnessecarily high) start with 3200Mhz Ram speed, tweak Ram later. Those two Volts might need manual tweaking to run 4133 and would still be a fair bit lower than auto.
If your cpu can't hold the 50x mulitplier in CB R15 and clocks down to lets say 47x then that would most likely be the -3 AVX offset in the bios. Hope EVGA offers seperate offsets for AVX and AVX 512. Try to find those and set them as desired. Just be warned they are there for a reason. AVX used by certain programs like Prime95 and R15 is very power hungry.
Then R15 is only very short load. You would usually not see VRM overheat on a short R15 run it takes usually a couple of minutes for them to saturate their little block. But they will definitely eventually overheat when using prime95. Might just put a fan on top. It's fine though during normal use.
The Mesh (formerly known as Cache might still be called like this in the bios) has a huge impact on this platform. It's worth raising it to 3000 since this should actually run at stock volts. sweetspot is 3200, that needs v1.1ish +/- 0.05v but Mesh hits a wall pretty soon after where volts won't help. So it's worth finding your sweetspot for mesh, since it also contributes to high temps.
Disclaimer: my experience is from the 7900X on an open testbench. I got my 7920X ready but EVGA can't make their mind up as to when to provide the X299 Micro in Germany.
The 7920X has a bigger die size which positively influences its ability to transfere heat between the die and the heatspreader due to a bigger surface area. But Mesh might need more volts, just work your way up. Nevertheless this chip is worth delidding, yours seems to be one of the better 25%.
Sry for typos, but I hope you get the idea, if you have any questions just ask.
post edited by Snipes7 - 2017/10/09 10:25:33