Yabai (https://github.com/koekeishiya/yabai) and skhd (https://github.com/koekeishiya/skhd) together makes a very powerful combination that works extremely well. It's as close to i3 as you can get on MacOS, and outside of a few odd things with 3 monitors I haven't run into any issues.
Yabai is actually the second iteration of tiling windows that koekeishiya has made and it's super well developed.
Seconding this; the only thing I miss from i3 is the fact that yabai almost by definition can't be better integrated with the OS, so there's a slight increase in latency that's barely perceptible but enough to make me notice how much zippier my Linux boxes + i3 are. Small price to pay for how much more comfortable they make me on macOS, though.
Same situation, I use ‘yabai’ on macos, which is similar enough to i3 for me.