I want to like TWMs but they all seem tailored to running single app workspaces on low res screens.
I would absolutely love a TWM that let me place/size windows like Spectacle or Rectangle but also _push_ other windows out of the way to maintain a grid and avoid overlapping. Open terminal, use keybind to place in upper right 1/3rd the screen width and 1/2 height. Open slack, hit same keybind, terminal gets pushed left (or down if there's already something to the left). Open browser, hit center 1/3rd 100% height keybind. Pushes terminal left. Focus slack, hit top right keybind again to expand window to 2/3rd width. Pushes browser down to center 1/3rd bottom 1/2. etc.
What you're describing is what tiling window managers do (or at least very close to what you're describing). Neither Spectacle or Rectangle are actually tiling window managers; they're just window snapping tools. I have never tried this (haven't used macos as my main OS in years), but I've heard it works well, and should give you the tiling window experience: https://github.com/ianyh/Amethyst