Some motherboards if you see auto as a voltage setting, right beside it you will see the voltage it is currently running at, you can lock it down by setting to manual.
Get your board manual out and read it.
@Bones or
@ShrimpBrime might be able to help
I'll try to put it into perspective best as possible.
So the "Boost" feature is a range, starting from P-state of 3600mhz and up to max XFR frequency single core boost of 4.2ghz.
When you are idle, you will almost always see the highest voltage while single core boost is activated and is how the Cpu reaches 4.2ghz.
The ALL core load will sustain a voltage (for the most part) and will continue to do so until throttle temp is reached at 95c.
Once you've hit the throttle temp, you should see the clocks drop along with the voltage.
If you do not reach 95c with your Ryzen 3000 chip and it still throttles, that will be due to overheating VRM package area. Mount a fan there.
While any Ryzen setup is set with stock values, the Cpu will protect it'self for you. You don't have to worry about it running 90c, even though that's just too hot even for my taste personally.
You can run the chip cooler, but won't impact performance while you have a stock setup.
When you manually overclock, you can pass the throttle point of these chips. ThermTrip is around 110c, the PC will shut right off.
Do take notice, the Cpu fan should reach 100% at 70c. This is the thermal alarm and will not reset until temps are lower than 70c. Some boards are dialed in at 60/65/70c respectively for ramping up the Cpu fan to 100%.
In short, there's no real worries I see here with the system. It's running as it should.
One way to keep it running cool - Leave everything on Auto but change only the multiplier to 36.25x manually. It will keep cpu voltage at max P-state for that chip. You do not need to disable PBO or anything like that, but you do have to add the extra quarter multi. If set to 36x, the system will act as normal boosting and what not.