Not seeing much difference in speed to be honest (and a lot more limitations), for example, if the Agenda share sheet comes up it will default to the last note you were at. Just hitting insert will append the content at the end of the note, also being smart enough to add a new line.
More importantly, I have tried many of these kind of sharing extensions in the past myself and yet always reverted back to the old workflow of sharing to Mail instead. Why? First because an append only (or even prepend or append choice) is just too limited, perhaps you want to add it in the middle of a list. Second, I found myself often wanting to add some content, for instance the date, or some extra words in front of what ever i’d share. Hence the choice for sharing to Mail instead, at least I could add some extra content.
Basically, my personal experience has always been that any sharing extension that forces you to revisit the same note again later to either move the inserted content, clean up some content, or add context to the share content, quickly becomes more hassle than it’s worth. With the sharing extension of Agenda when you’re done, you’re done, with the shared content at the right spot, a checklist item checked off, some extra context added etc, no need for follow ups.
Tot tries to partially get around this by offering a limited set of choices, like prepend or append, and some formatting choices, but I doubt that it would be enough for me to ultimately find it easier to just switch to the app itself.