I'm giving atuin a try right now and the first thing I noticed is what you just said about the up arrow. I don't need to invoke the full atuin command history screen when I just want to quickly edit the last command. In its default state, the up arrow does the same thing as ctrl-r so it isn't particularly useful, in my opinion. The developer suggests making it more useful by setting the up arrow to invoke a "local" command search, meaning a search of commands that were used in the current directory. Alternatively, you can disable the remapping of the up arrow key and just invoke atuin using ctrl-r. I think that's what I will try next.

Having automatic updates as opt-in by default would be better to avoid supply chain attacks.

I guess the majority of users would prefer automatic data synchronization. The tool therefore offers the option of deactivating automatic synchronization (https://docs.atuin.sh/configuration/config/).

Also, if the original history file is still there it would be a good feature to be able to diff between the sqlite and the history file to see if commands have been deleted.

A solution can probably be created with https://docs.atuin.sh/reference/list/ in conjunction with a shell script.

Are there options to choose what encryption algo is used?

I suspect that this is not possible. Why do you want to change the type of encryption?

Based on https://docs.atuin.sh/configuration/config/#search_mode, "fuzzy search" is used as standard.

The searching TUI is so similar to fzf that I think it might even be fzf. If it's not, it's just very similar.