Hide the unnecessary help message on the top of the completions buffer.

(setopt completion-show-help nil)

Enable efficient vertical scanning by showing completions in a single column and in a window with a constant height.

(setopt completions-format 'one-column
        completions-max-height 16)

Do not wrap long lines, that is truncate lines, in the completions buffer

Note.  Wrapped lines make tabular data, such as bibliographic references in Citar, do not look like “loose tea”.

(add-hook 'completion-list-mode-hook
          (lambda ()
            (setopt truncate-lines t)))

Sort completions by their position in the minibuffer-history.

(setopt completions-sort 'historical)

Update completions eagerly.

(setopt completion-eager-update t)