[1] https://github.com/kovidgoyal/kitty/issues/887#issuecomment-...
[1] https://github.com/jwilm/alacritty
Disclaimer: I am not associated with the project in any way. Just a fan.
> This appears to be an issue outside of terminal emulators; either macOS has an IPC performance issue, or either tmux or vim (or both) have a bug. This same issue can be seen in iTerm2 and Terminal.app. I've found that if tmux is running on another machine which is connected to Alacritty via SSH, this issue disappears. Actual throughput and rendering performance are still better in Alacritty.
There's an older HN thread [1] on the subject with benchmarks and lots of interesting chatter. It's worth a read IMHO.