Sure, Karin is featured in the Boruto manga. Her role may not be as prominent as in some other arcs, but she's there contributing to the overall narrative.
Manga is made by a team of creators. First, a story is conceptualized by the writer. Then, the artist sketches the characters and panels. Colorists add color if needed, and letterers add the text. Finally, it goes through editing and proofreading before publication.
Well, popularity can be subjective. However, series like 'Demon Slayer' and 'Attack on Titan' are generating a lot of buzz right now. They have engaging storylines and well-developed characters that attract many readers.