I read on PC, how can I save power and make PC last longer by under powering the PC ?
On Windows I put max CPU state to 1%, PCIe and WIreless Power to power saving mode.
Also related question, How to disallow software from inhibiting power management?
You can use cpupower to enter different states of power limits. The link is to the arch wiki but I’d bet it’s in your package manager for you to install.
https://wiki.archlinux.org/title/CPU_frequency_scaling
Not sure about the second question.