Smart Update Question
 

A few days ago I needed to access my backup drive, which I always use smart update for. By accident I think I might have changed a file or two in the backup while I was opening up different files. Since the files on my backup now have a more recent modification date compared to my source, does that mean superduper's smart update will not overwrite those backup files until the same source files have a more recent modification date? Or does superduper overwrite the backup files with my source files due to them being different in some way and the dates are ignored?

Smart Update copies files if they're different, so it will overwrite the data as you'd expect.

So basically, if I change any files in my backup, SD! will automatically overwrite them with my source files during smart update?

Yes. As the description of Smart Update says pretty specifically, it makes the changes necessary to make the destination match the selections from the source.