I'd also be interested in it. I got a work laptop that has a good battery, but it's an i7 and I mainly need to SSH and use FF, so I think I could undervolt/underclock quite a bit.
Ubuntu has some pretty sensible presets for that, I use them by default when I'm on battery. It's called power profile and there is performance, balanced, and power saver. The only application where responsiveness really suffers is gmail 🤡
Pretty sure those are present in other distros, too. My understanding is that they really just limit per draw.