My understanding is that it's not really the disrto, but the software running on it that'd effect battery life and performance. Both Debian and Arch can come pretty bare bones on a blank install (Ubuntu and derivatives tend to come with a fair bit of stuff bundled out of the box).

I'd personally reccomend trying a Debian installation (I'd likely say use stable, but testing or sid are also options if you need quicker updates and don't care for flatpak/snap/appimage/distrobox). The installer plays nice with Windows, and you can skip installing a desktop during installation then CLI install a tiling window manager to really minimize 'bloat'.

Add tlp package for battery life. And any major distro should be fine really

🧌 NixOS 🧌

I use xmonad/polybar/rofi/alacritty/fish with Home Manager and flakes. You could just use my whole config and have it up and running in a day, deleting lines and adding others. Fork it and modify it to meet your preferences (as I did when I forked this amazingly slick config). I even made a custom typeface to add my favorite crypto logos to my Polybar.

Debian is solid. You probably don't want to have to fuck around on a laptop that you're using primarily for getting shit done. Flatpaks can handle most of the extra shit you'd want to use. That said, I used to be an Arch guy for years too, and if you're comfortable with it, it's fine to use, but you'll run into the same kind of annoyances. Not true breakage usually, but eventually I got tired of having new surprise bugs in shit that was working fine before.

Also I can't be sure, but I suspect Wayland is probably better on energy draw since it should be more efficient. Maybe try sway for your twm?

I guess you can run fedora if you want full features of a laptop. Im currently running LMDE5, is rock solid for me this past 2+ years, upgraded seamlessly from LMDE4. I guess LMDE6 will be released soon after LM 21.2 is released. I do think that at the end of the day , whatever you choose, you can change your desktop environment so it suites you.

specifically battery life for my University classes

try undervolting your CPU/GPU. That was the first thing I did when I got my thinkpad and it improved the thermals and battery life significantly.

Yes, the best distro I always recommend is Fedora Silverblue, especially the KDE version: Fedora Kinoite. I hate this naming scheme though.

Sadly Fedora is controlled by Red Hat and it may get killed off soon.