Yes, You can find some good stuff on searching you can also try in Sarojni Nagar as its a little more trendy and big market for such stuff janpath is more on a bohemian style
Yes you can buy but there are chances that you might not see a lot of variety and also the stock at all the vendors might be the same so just keep other options open also
Janpath is more of an ethnic attire market.. you can look for party wear stuff in Sarojini and Lajpat!
Try out Myntra as well.. great stuff and good quality products too