[Resolved] Change default language, with new default as the original for existing content

Hi dear people at WPML,

I'm a fresh subscriber to WPML, with an Elementor website currently in Dutch.

I want to add English, switch to English as the default language, and somehow make sure that English pages and posts will be treated as the "original" language, so that when I add more languages in the future, the pages can be translated from English to those languages.

I've already found several topics and discussed the matter with one of your colleagues in the "pre-sales questions". I would like advise on the strategy to follow. I have three avenues I'd like to explore. I will explain them below; I hope I can make myself clear enough for you to understand me, and to advise me on the best course of action.

I. The easy strategy (I think)

1. Translate existing pages and posts into English (I won't translate all; many will be in Dutch and remain in Dutch)
2. When happy, switch the default language from Dutch to English, and accept that for all existing content, I will only be able to use the translation editor to translate from Dutch, OR translate the pages and posts that were originally written in Dutch, using the wordpress editor instead of the translation editor.
3. Customize the menus for each language.

II. The more cumbersome strategy (I think):

1. Switch the default language to English.
2. Create new posts and pages and populate them with English content.
3. For every post and page, add a Dutch translation, and paste into that translation the Dutch content I copied from the Dutch original post / page.
4. When happy, delete all the original Dutch pages and posts (except the ones I will leave only in the Dutch language), making sure that the translated URL slugs match the ones from my original Dutch pages (so that I don't get any broken links).
5. Customize the menus for each language.

III. The strategy that's also possible?

1. Switch the default language to English.
2. If possible, duplicate pages and posts from within WordPress, so that not just the content, but also the Elementor layouts are copied (make-or-break question: will these duplicates be treated by WPML as "English original" posts and pages, even though the content is written in Dutch, because I switched the default language to English?).
3. Replace the Dutch content in the newly created duplicates with English content.
4. A a Dutch translation to each new duplicate, every time populating the Dutch translation with Dutch content that I copy from from the original post / page.
5. When happy, delete all the original Dutch pages and posts (except the ones I will leave only in the Dutch language), making sure that the translated URL slugs match the ones from my original Dutch pages (so that I don't get any broken links).
6. Customize the menus for each language.

My website is Raymundo.earth.

I look forward to your reply, thanks for your help!

Raymundo