OK then, grab a Raspberry Pi 3B, 4B and Zero, pop open these docs for config.txt, and try and figure out how far you can push each of these tiny machines: https://www.elinux.org/RPiconfig
Really though, the RPi's config.txt is exactly this kind of rabbit hole. I just got a Zero W today and now I'm thinking about if it's possible to underclock it enough to power it with a lemon battery via GPIO.
I have more fun with Arduino type boards than RPis. For me, RPis are just fun to see where you can put a little computer, but I like all of the soldering, bread boarding, wiring, etc of the various shields in the Arduino realm. I get the best of both worlds with the analog/digital inputs, plus the programming in a very limited (requires some creativity) fooprint type of challenge. I haven't messed with the GPIOs on a RPi though, but now we're back to just programming in whatever unsconstrained/unrestricted way of a desktop. ??? we all like different things.
Really though, the RPi's config.txt is exactly this kind of rabbit hole. I just got a Zero W today and now I'm thinking about if it's possible to underclock it enough to power it with a lemon battery via GPIO.