Safe voltages is not really a thing for Ryzens the way it is for Intels. Intels are not a dynamic cpu as such, so setting a single voltage that covers all cores at any use is fine, even preferred in OC cases. But Ryzens differ, you'll see voltages of upto 1.5v used for a single core bump, which lowers amperage needs for that core, but bump that upto multiple cores and you'll see much lower voltages in the 1.2-1.3v range. So setting a fixed voltage of 1.3v is going to hurt single core performance but could also be too much for all core use.
So what is safe? Many early Ryzen adopters who did OC thinking they were safe, burned out cpus in less than 6 months, by applying a roughly 1.325v fixed.
That's one reason I prefer CT2, it doesn't change or set vcore (SVI2) use, it limits VID instead. That changes what the cpu Can use upto, not setting what the cpu Will use always. It allows the Ryzen to decide for itself what it needs in reality, not what it can get away with demanding, used or not.
PBO changes power limits. If you are pushing the 90A power limit and that's forcing the Ryzen to throttle back to stay inside the limit, then PBO is going to set the cpu free to go beyond that 90A. Doesn't mean it's going to Use that amount set. The MSI Godlike and Gigabyte Master can set that limit to 1000A. There isn't a Ryzen made that'll ever come remotely close, those boards are set to erase any possible limitations, even using LN2.
So use of PBO isn't going to give you any further performance as such, it just extends the power limits so that they don't become a limiting factor in the performance desired. Factory PBO just sets the limits at AMD set limits, which raises the range of what the Ryzen deems as tolerable. PBO 1 or PBO 2 etc don't use AMD set limits, but motherboard vendor limits.
If you are not hitting 100% of the power limits, raising them by bios or Ryzen Master isn't going to affect performance at all.
But a lot depends on how you view performance, a personal opinion. For Ryzens, they'd prefer you to get lower fps for an hour long gaming session and stay inside its deemed safe limits, than to get the extra few fps by pushing limits and possibly doing irreparable damage and bsod after 10 minutes. Intels will give you want you want now and deal with the consequences later.
A Ryzen will do what it has to to keep you out of 90ish °C ranges, an Intel will happily let the cpu sit in that 90°C + range, it's on you to supply the cooling necessary to lower it.