I have not bought any Huananzhi boards, so no experience there. As far as I can tell, only some of the very first high-grade Chinese X99 boards could increase VDDR from BIOS. But once you start to get low enough RAM latency/timings, you get diminishing returns, at least in my own experience (gaming focused). Hardware Canucks had a great video recently, where you can basically slot in your overclocked X99 system somewhere between Ryzen 2xxx and 3xxx (closer to 3xxx). Here is a AMIBCP screenshot of what a finished RAM tweak normally looks like (second hand Samsung ECC RAM). The only thing that is a bit higher than usual is tFAW, due to aggressive automatic tuning of tRRD_L (which in turn forces a high tRRD setting).
If you absolutely need to increase the DDR4 RAM voltage, then I think hardware mods are the only way forward. You can search for “motherboard volt mod” and prepare to dig and learn a lot.