Thanks for the feedback!
meytho when I now open documents, how exactly does this work?
When an encrypted file is opened, we obviously need to decrypt and hand out a decrypted state of it to the Files app so other applications or the preview can access the files and show their content to the use.
meytho It’s a local unencrypted version saved on my iPad? If so, for how long?
This decrypted file will be removed automatically once the Files app notifies our app that it is finished working with it.
meytho To save space on the iPad, do I need to manually delete files locally at one point? And can I securely do so?
All downloaded files will be saved to a local sandboxed and encrypted cache. So there is no possibility but also no need to purge any local files. The system will take care of purging files on demand. If you think that this doesn't work as intended, feel free to reach out to us.
meytho And if I make changes to a file, will these be uploaded automatically? What if I open, say, an excel file with Axel, having autosave on, will it be uploaded to my secure box crypto space on my OneDrive account?
Yes - this is exactly why we decided to go all-in with the Files app. You can seamlessly work with your files and all changes will be propagated back automatically through the Files app integration.
This works with all apps that usually save their content using the Files app - including Excel.
I hope this answers all of your questions - if not, don't hesitate to ask!