

If that’s the case then I believe just controlling notifications for those two apps for each focus probably gets you what you want. Then also go to iOS Settings > Outlook > and disable the authorization for it to use Time Sensitive Notifications. I have a similar setup on my devices.
Why write off iCloud? Just turn on the advanced data protection feature for end to end encryption.
If you want to self host, while I’m not familiar with Goodnotes I bet you could write a simple Apple shortcut to take those files to a storage provider like nextcloud then just automate that shortcut to run daily, weekly, whatever.