Everything stays on your server

No. Folders, clean-up, alternative texts and the provenance check work with the file on your server and write into your database. The plugin goes out to the network only in places that have nothing to do with that: the license and update request to kakapowp.com, a request via “Help & support” that you send yourself, and, if you set them up, the connection to your own Remote Sites. With the request go your text, the attachments you choose yourself, the name and email address of your account for the reply, and the diagnostic details shown, including the license key, unless you deselect them. The connection to the Remote Sites carries only numbers, switches and the address of the installation — no image and no file name.

No. Not for the alternative texts either: the suggestion comes from the title or file name, not from an outside service.

You decide beforehand under “Your data” whether settings, findings and folders go with it. The image files stay in place when you uninstall, and so do the alternative texts — they belong to WordPress. Media only ever changed a file where you wanted it to: when replacing, when renaming and when deleting orphaned files.