I had good experience with BorgBackup and restic. However, I've settled with restic since it had the right back ends for me that Borg did not have and I rather like it's just one static binary instead of Python+C.
As far as I can see, BorgBackup has a bus factor of one while restic has two to three active contributers.
Other than that, they are quite comparable, I think.
Unfortunately with iOS you are stuck with Obsidian Sync because Syncthing does not work because of the permission model. Otherwise I prefer Obsidian over Joplin for the above mentioned reasons and nice extension ecosystem. It's easy to get your files out of Obsidian, no vendor lock-in