I use AutoFocus which gives focus-follows-mouse with AeroSpace and its a good enough replacement for i3wm.
Extremely thankful for both projects.
There's also https://github.com/sbmpost/AutoRaise which is open source. AutoFocus seems like a proprietary clone in beta that will eventually become paid.
One issue: If an app uses native Mac tabs, Aerospace treats each tab as a window, which completely breaks the full screen functionality. Alacritty is one example. It’s really odd.
Edit: there’s an open issue for this: https://github.com/nikitabobko/AeroSpace/issues/68