My wife and I have our pcs in the same room. An extra 100w+ watts added to each one can ratchet the temp of the room up.
It's like having an extra person or two in the room, and I think everyone who ever had a party at home knows what that does to the temperature of a smaller room, then most computers are designed to purge their excess heat into the air.
intel recently also used to have the buggy atoms that'd just fail eventually because of some internal aging process. I don't remember the specifics, but the particular SoCs affected could be revived by an external pullup resistor. Intel has a bit of a history of such problems.
I also really like the idea of low energy systems, and electricity in my parts is expensive enough (soon to be even more expensive) that power draw of the computer if you use it regularly is actually noticeable in the bill. My Desktop system (4650G Pro) currently manages to do 25W (measured at the socket, including the monitor which gets supplied via USB) if I do stuff like writing this post, which is pretty good for a full system with dedicated GPU and everything. Naturally, a low power consumption like this also gives you a system that is completely silent in normal desktop operation. I accept some little fan noise in heavy loads, in normal OS operation I'd not put up with it anymore. These times are just over over. It's also nice to have a computer that's silent and produces no noticeable warmth when browsing, watching videos or doing some light gaming.
The trick is mostly to use solid state storage, and a low TDP SoC with iGPU. Then undervolt what you can. dGPUs are not really optimized for low power usage and will happily burn several times what the entire rest of the system consumes just to e.g. play back a video. (and the video won't be played back "better" or anything) If you want to go farther than that, you need to go ARM or Notebooks which are built for low consumption. There's big caveats with both and I personally find a proper x86 desktop with exchangeable standard parts endlessly more useful.
In theory a more performant, higher TDP CPU might actually consume less by doing the same tasks at lower clocks snd quicker (= rush back to sleep), in practice software is often shit and the more oomph the CPU offers, the more it'll be utilized, even if there's no subjective improvement in operation. Most OSes CPU governors are also not smart enough or just don't have enough information to make good decisions at most turns and the school of thought to design your OS to be power efficent is also kinda new. Windows here is actually a lot better and I say this as a ~20 year linux user. For power consumption, Linux sucks.
Modern processors allow you to set TDP envelope targets, at the cost of performance. This is sort of the brutal method, but always works as the decisions how to hit the target are mostly made in the firmware/microcode and not by the OS. There is some value in setting up different TDP profiles for different workloads but I haven't experimented with it much yet. (Again, theoretically this should not be necessary, in practice all software sucks) This is usually more to regulate how much heat the chip produces, not to regulate power consumption, mind you. The power consumption is the side effect.
It's a complicated topic you could write books about, really, especially since the hardware has become so complex. For example I have a cheap N4020 Notebook. It does most of the things I want from it fairly well at a very low power consumption, just more complicated DosBox emulation sometimes was a bit slow, with the higher end DOS games. Eventually I figured out by disabling the second CPU core (not really, just putting it offline in linux so it doesn't get any tasks anymore and can go into deep sleep) DosBox would actually run quicker since the whole SoC wouldn't heat up as much with the second core, allowing the other core to stay at boost states almost indefinite. Things like that are just really hard to account for as general rule.
