Name

Pacer and fzf-tab

In short

fzf-tab replaces zsh's completion menu with the fzf fuzzy finder: press ⇥ and pick from zsh's own completions. Pacer opens a popover next to the cursor while you type, without a key press, and fills it from Fig completion specs, git, and the tools' own --help.

Where they differ

When it opens
fzf-tab opens when you press ⇥. Pacer opens as you type and updates on every key.
What it lists
fzf-tab lists what zsh's completion functions return. Pacer lists what its specs describe, with a description on every row, and puts changed files and recent branches first.
Where it runs
fzf-tab works in any terminal that runs zsh. Pacer needs Ghostty, iTerm2, or Terminal on an Apple silicon Mac.

Which to choose

If you like pressing ⇥ and fuzzy finding, fzf-tab fits well. If you want suggestions to appear by themselves, with descriptions and git-aware ordering, try Pacer.