When Joplin went from AES 128bit encryption to AES 256bit, I went through a lot of my notes to make minuscule changes (add a blank), in order to force re-encryption. Today I see that the coming pre-release (2.12.15) will "temporarily" go back to AES 256 because of perceived performance issues. For once, I didn't notice any performance issues (using nextcloud) at all, at least not on a desktop. On the other hand I have declined the above mentioned update, so my notes will remain encrypted with AES 256. Other may have had the same idea.
So why am I reporting this ?
I would just like to indicate that "several" forth and back switches between AES 128 and AES 256 might be less than ideal for some users, regardless of the fact that others report performance problems on slower devices.
We've added a way to reencrypt all the notes in the next release so the good news is that once we address these performance issues and enable AES-256, you won't have go through all your notes again to reencrypt manually.