vertico-posframe is an vertico extension, which lets vertico use posframe to show its candidate menu.

NOTE: vertico-posframe requires Emacs 26 and do not support mouse click.

(require 'vertico-posframe)
(vertico-posframe-mode 1)

(setq vertico-multiform-commands
      '((consult-line
         posframe
         (vertico-posframe-poshandler . posframe-poshandler-frame-top-center)
         (vertico-posframe-border-width . 10)
         ;; NOTE: This is useful when emacs is used in both in X and
         ;; terminal, for posframe do not work well in terminal, so
         ;; vertico-buffer-mode will be used as fallback at the
         ;; moment.
         (vertico-posframe-fallback-mode . vertico-buffer-mode))
        (t posframe)))
(vertico-multiform-mode 1)

NOTE: vertico-posframe-mode will be activated/deactivated by vertico-multiform-mode dynamically when you add ‘posframe’ setting to vertico-multiform-commands, please do not enable vertico-posframe-mode globally at the moment.

(setq vertico-multiform-commands
      '(
        (consult-line (:not posframe))
        (t posframe)
        ))

(setq vertico-posframe-parameters
      '((left-fringe . 8)
        (right-fringe . 8)))

By the way, User can set any parameters of vertico-posframe with the help of `vertico-posframe-parameters’.