Lots of great suggestions here. I still use Xorg as I've just been lazy in regards to this. I like minimal RAM usage for everything on my systems regardless of how much is available, so I ended up with bspwm. Technically DWM is lighter, but having compiled and used the suckless terminal as my daily terminal emulator, i can honestly say I'd rather just stick with bspwm for this part of my system.

I started on Xfce, but kept on trying to make it act like a TWM, which is when I took the dive in and started using i3. i3 was a very good intro TWM, but I didn't like how I had to install a python package to get it to tile in a Golden Ratio format, and found that bspwm did that out of the box. Additionally, bspwm is configured in bash, which makes it very versatile when used with bash scripts, so I'm still with it and happy.

Whenever I do eventially moce to Wayland, I'll be looking for the lightest weight (in terms of RAM usage) TWM and terminal emulator possible. I've already played around with Sway on my Raspberry Pi 4 and have heard good things about the foot terminal, but still don't know much else about the available options on Wayland yet.

I will note that TWMs changed my entire workflow and imho is just faster and better than most DE workflows I've seen (though there are exceptions).

This is thanks to my initial interest in creating a seamless workflow involving neovim, vimium, bspwm, and a 40% plank ortholinear keyboard. That combo in particular made it so some people who watch me work get nauseous, lol. Now if only my speed of thought could catch up...

Anyways, enjoy the journey, TWMs are powerful tools once you get the hang of them.