The best way to update existing Paragraphs in Production with newField = TRUE

If you are using config sync just setup the prod site in your local and make a config export and commit all the config changes.After that make the necessary changes to the paragraph fields and make a config export again and commit them. Now move all the config changes to production and make a config import and clear cache. Now you will have new field in the production.

If you are not using config sync I would suggest you to make a config export of the new field and create a custom module and include the exported config in the config/install directory of the module and install that module on the production and clear cache you will have your new paragraph field.

I believe the check box value also will be set while config import. If the value is not set , as paragraph is an Entity use Paragraph:load function and update the field values through batch.