“Adding/removing string” simply checks if a change contains the string verbatim. “Changing lines matching” on the other hand applies the given pattern as a regular expression and finds changes which match the provided regex pattern.
The corresponding command line options are -S
(adding/removing string) and -G
(changing lines matching). On the command line, you also have the possibility of -Sstring --pickaxe-regex
which will treat the pickaxe string as a regular expression, but only match it, if it is either deleted or added in a commit (but not if it's only part of a changed line).