The reason I switched from iTerm2 is it took multiple seconds to resize a window on macOS. I use Rectangle to resize windows, and by default my shortcut for "put this window on the left half" cycles through window sizes when the window is already on the left. So a common workflow is to tap Hyper-J to move a window to the left half, then make it the left third, then the left two thirds of the screen. This is fine for any text editor or browser, but iTerm2 would beachball while I waited multiple seconds for it to resize the window.

Wezterm moves instantly.

No, iTerm is not slow. Ghostty is not noticeably faster in any of my workflows. I am sure Ghostty is faster in some use case, but it's nothing I regularly do or have noticed.

Same, I use it all the time and never perceived it as slow. I am not a tmux user, maybe the speed is noticeable when using more complex terminal apps like that?