I've tried playing with all the power options, including Passive vs
Active mode, Min/Max CPU, ensuring power management is enabled, etc.,
but nothing makes the CPU dip at all (I'm watching it with Resource
Monitor and CPU-Z).
That is normal, and a common misunderstanding of how Windows’ CPU throttling works.
You can set the maximum CPU load by adjusting the Maximum CPU State setting and the system will then reduce its capabilities to act like it has a slower CPU.
It sounds like you were expecting the CPU load level to be capped and no longer reach the top of the graph. This is not what is happening. Rather, when you throttle the CPU, the graph is recalculated so that the top is now set to whatever percentage of the CPU’s full power you set it to. Therefore, if you are running a program that puts 100% load on the CPU, the monitor will not show the load lower than before, it will still show it at 100% on the graph because it is still using 100% of the CPU, it’s just that the CPU’s maximum has been reduced.
Think of it as one of those telescopic travel-cups; you can adjust how big or small it is by changing how many rings are up. Regardless of how big or small the cup may be, filling it up will still make it full; you are simply redefining what “full” means.
Run a temperature-monitoring program like SpeedFan, then run a program that puts 100% load on the CPU. Naturally, you will see the temperature rise. Then you can adjust the Maximum CPU State setting and watch as the temperature drops. You can lower it more and see the temperature fall further. If you then increase the max state, the temperature will go up a corresponding amount.
If you also set it to passive cooling, then after a while, the laptop should no longer make any noise.
However, you will also want to reduce the CPU load as well because by throttling the CPU, you are making it so that whatever work the programs are trying to do will take longer because there is not as much processing power available. You should try to eliminated as many programs as possible so that whatever you are running at night will be able to finish quicker. (If you are not running anything and it’s idling all night, then you should just put the computer to sleep at night for numerous reasons.)