1 - My experience is generally positive Weaver, it brings automated overclocking to the masses.
2 - This depends on how the hardware is configured (mainly bios) and also on things like power draw and heat. My intel 9900k will stay pegged at max clocks forever, as I have set ridiculously high boost parameters and have a high end cooler on it. Of course this means the cpu runs out of spec in such a scenario. My Ryzen 2600X I have it on stock configuration, it will generally be able to keep at its max single core boost clock for a very long time as it doesnt heat the cpu up much or drag it to its power limits, but a all core overload will after a short time slightly downclock, but noy by much though, still at turbo clocks, just not max turbo clocks.
Bear in mind real world loads will keep clocks higher for longer as not many real life workloads will peg maximum load sustained.
3 - Ambient temperature impact will depend on bios configuration and how effective the cpu cooling is.
4 - I have dynamic fan speed, used to use performance profile but now on balanced, most modern PC's now have dynamic fan speeds using PWM connectors.
Additional Notes.
Many cpu's will default to an over voltage, which is because each cpu is different in terms of the quality of the silicon and boards are configured to make sure the worst cpu's work. If you get a better than a worst cpu, you can decrease the voltage, which in turn decreases heat and power consumption, my 9900k defaulted to 1.36v, I run it at 1.25v and it runs around 20C cooler and uses about 40W less under full load.
Also on ryzen's if you disable the turbo boost (XFR, stands for extended frequency range), you get so much better power efficiency, its diminishing returns as clocks go up which is why turbo clocks are not standard clocks, my ryzen at 3.6ghz uses about 60% power as it does in XFR at 4.15ghz.
I feel AMD have done it better, manual overclocking on the ryzen's give you very little improvement over the automated configuration, whilst bigger gains can be had from intel although in their latest generation chips the overclocking headroom has reduced, so they getting there as well.
On my pfsense unit which has an i5, I looked for the power/performance sweet spot, it will downclock as low as 500mhz if you let it, but I observed the voltage and heat at 1200mhz vs 500mhz isnt that different, and then it starts rising rapidly above that so I set the min clock on that to 1200mhz, and set the p-states to a less aggressive configuration so it only ramps up when under sustained load instead of brief spikes.