To what extent does gender shape female career choices and identities?
This depends on how you are using the term "gender." If you are using it to refer to a biological fact, then gender only shapes female career choices to a relatively small extent. There are a few kinds of jobs that are closed to females by virtue of their biological sex. These include jobs such as that of infantry soldier and (to a great degree) professional athlete. But there are not many other kinds of jobs that are closed to women because of biology.
If you are using this term to refer to the way in which society conceives of what women "should be," then gender has a much greater impact on women's career choices. Women disproportionately go into careers that involve caring for others. They are nurses or day care workers much more than men are. The vast majority of elementary school teachers are women. These are jobs (unlike, for example, policing or carpentry) that are seen as compatible with what our society thinks that women should be.