Re cooler requirements (speaking from the theoretical POV, as I am
still not a Zen2 owner yet):
AMDs processors are strict about the sustained power usage. Normally sized coolers should have little trouble at constant 100 % use at stock (unless the BIOS vendor applies an overvolting by default).
Of course the tiny 7nm transistors will cause higher peak temperatures than on comparable 14 nm processors. But that's just a sign of higher
heat flux density, not of higher power use.
Oversizing the cooler a lot may help a little with sustained throughput though, as the processor will be able to crank up the clocks a little more.
Temperatures are with in reason then?
The Ryzen 3000 processors are specified for 95 °C operating temperature.
The reason I ask is I have been switching from AIO to Noctua coolers. I have been leery of possible pump failures (knock on wood I have never had one) thus the switch to air coolers- My thought is there would be some passive at least on air if the fan/s stopped for some reason vs a pump failure
If the cooler fan fails, the processor will continue to work at much reduced clocks.
The internet is all abuzz due to a test of a Youtube celebrity without any cooler at all, in which an Intel system kept working at low clock but an AMD system shut down. But this mode of operation is not representative of systems with a passive cooler mounted.