shmoel “Is Simcha both a boys and a girls name?”
Ashkinazim use Simcha for boys while Sefardim use it for girls.
Likewise, the OP should be aware that Sefardim give children names after their living parents and are not choshesh for anything.
shmoel “Any other names that are shared by boys and girls?” There are several, such as Noah. There is also names with variations such as Boruch and Brachah, Chaya and Chayim.
Of interest to me is the historical evolution, that it is fairly “modern” the common practice to give a child more than one name, contrary to our tradition for nearly two thousand years that we only had one name (with certain exceptions like Yisro who had many names – but not used at the same time, and Moshe who had another name from his mother etc.).