Hi,
Thank you for supporting the project.
You only need an Ultimate plan, so S3Drive can fetch your license and enable you all of the premium features.
On top of that there is a testing account associated with your user account, so you can test the app on a real S3 storage before you buy the app.
No matter what you do you can't lose any Ultimate features, especially when my records show that you've bought an lifetime license that never expires.
Please find couple screenshots which indicate how you can set up S3 credentials after you've logged in using managed / Ultimate account. (edited)