I also came from a TWM (i3) to macOS. It took a while to get to a good solution but I have it down now with yabai and skhd for window management. For launching apps, I wrote something around the launchAppOrFocus API in hammerspoon, assigning hot keys to my commonly used apps. I also have a rule set in yabai that launches certain apps in set desktop spaces.

I use spotlight search for the apps I don’t open so frequently but having something closer to dmenu (or a fuzzy find app picker) would be nice.