What is the best Emacs workspaces plugin?

Personally, I've been using `persp-mode':

Perspectives for emacs, based on perspective-el by Nathan Weizenbaum. But perspectives shared among frames + ability to save/restore from/to file.

I use a combination of save-visited-files and workgroups. In fact, workgroups will probably do most of what you want by itself.

My config:

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;;; workgroups for windows

(setq wg-prefix-key (kbd "C-c z")
      wg-no-confirm t
      wg-file (concat emacs-persistence-directory "workgroups")
      wg-use-faces nil
      wg-switch-on-load nil)

(defun wg-load-default ()
  "Run `wg-load' on `wg-file'."
  (interactive)
  (wg-load wg-file))

(defun wg-save-default ()
  "Run `wg-save' on `wg-file'."
  (interactive)
  (when wg-list
    (with-temp-message ""
      (wg-save wg-file))))

(with-library 'workgroups
  (define-key wg-map (kbd "C-l") 'wg-load-default)
  (define-key wg-map (kbd "C-s") 'wg-save-default)
  (workgroups-mode 1)
  (add-hook 'auto-save-hook 'wg-save-default)
  (add-hook 'kill-emacs-hook 'wg-save-default))