1.5 is what AMD has said is the max. Past that is supposed to be assured damage outside of small bursts. But I'd agree 1.45 is a good upper margin, for board/sensor variance. Though its kinda moot as at the point where youre seeing that kind of voltage sustained temperatures are probably going to be up there anyway. Generally Ryzen is temp/clock limited... under normal circumstances.
DDR4 is pretty voltage tolerant relative to its standard base voltage... funnily enough it is also 1.5 though generally I think people only dare to go there for benchmarking. Additionally different modules have different sweet spots for voltage, so quite often it isnt a simple matter of enough voltage--too much can be a detriment, even if it is safe. Say youre going up incrementally when you hit a point where it boots. Stability may improve with another tick or two more. And another tick or two past that it will start to drop off.
Some DRAM loves the voltage, others just can't do it. B-die seems happy to go right up to 1.5 so long as its running fairly cool. Some micron and hynix variants will not post past 1.4v.
Point is keep the number in mind but you shouldnt have to worry about hitting it. If you get a good board and good RAM you should be able run good XMP/DOCP settings with little to no tweaking and get there with not much more than 1.4v and 1.1v SOC max. If you find yourself going further just to boot or whatever youre entering territory where it gets really hard to achieve lasting stability. Itll take more than voltage. Configs requiring that kind of juice also tend to require the best board, best modules (eg b-die,) golden IMC... ...with anything but the best stuff theres typically no point surpassing 1.4ish and running overclocks that actually need more than that.. Good, balanced settings will typically require ~1.35v. Maybe a little more.
Semi related... RAM overclocking with Ryzen is a huge rabbit hole. If you're not into tackling a whole lot of tedium and study, I dont think its worth the trouble. On any decent X470 b-die will run DOCP at 1.35v easy, unless theyre rated for >3600 or something. At a minimum it'll all pretty much do 3200 CL14 with little to no tweaking depending on the flavor.
