st. It just works. I’m always opening and closing terminals, and 90% of the stuff I use have’s a TUI. st launches before I can even notice, under 4GB of RAM, and the entire install is less than a MiB.
I think they’re talking about the tandem of tiling and workspaces, as usually you can customize your tiling per-workspace. Some TWMs have tags instead of workspaces, making it even better.